Add F4SE plugin template

Create a minimal Fallout 4 F4SE/CommonLibF4 starter repo with build, packaging, install, and rename scripts, plus initial plugin source, headers, and xmake configuration.

README.md

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+# F4SEPluginTemplate
+
+Minimal reusable Fallout 4 F4SE plugin template using CommonLibF4.
+
+This template is intentionally lightweight. Add project-specific dependencies such as Ultralight, GameNetworkingSockets, ImGui, or custom SDKs inside each actual mod repo instead of adding them here.
+
+## Requirements
+
+- Windows
+- Visual Studio 2022 with C++ tools, or another MSVC/Clang-CL C++23 toolchain
+- xmake 3.0.0 or newer
+- Git
+- Fallout 4 Script Extender installed for testing
+
+## Create a new mod repo from this template
+
+```powershell
+git clone <your-template-repo-url> MyNewF4SEMod
+cd MyNewF4SEMod
+git submodule update --init --recursive
+.\scripts\rename-template.ps1 -NewName "MyNewF4SEMod" -Author "YourName"
+```
+
+Then commit the renamed version as the starting point for the new mod.
+
+## Build
+
+```powershell
+xmake build
+```
+
+The built plugin is copied to:
+
+```text
+package/F4SE/Plugins/
+```
+
+## Generate Visual Studio project
+
+```powershell
+xmake project -k vsxmake
+```
+
+## Package for mod managers
+
+```powershell
+.\scripts\package.ps1 -OutputName "MyNewF4SEMod"
+```
+
+This creates a zip with the expected layout:
+
+```text
+F4SE/Plugins/MyNewF4SEMod.dll
+F4SE/Plugins/MyNewF4SEMod.pdb
+```
+
+## Dev install to Fallout 4
+
+```powershell
+.\scripts\install-dev.ps1 -Fallout4Path "C:\Program Files (x86)\Steam\steamapps\common\Fallout 4"
+```
+
+## Repo layout
+
+```text
+src/                  C++ plugin source
+include/              Public/internal headers
+ThirdParty/CommonLibF4/      CommonLibF4 submodule
+package/              Staged mod-manager package output
+scripts/              Helper scripts
+```
+## Optional Modules
+
+This template intentionally keeps the base plugin minimal. Only add extra third-party modules when a specific mod needs them.
+
+The recommended convention is to place optional dependencies in `ThirdParty/`:
+
+```text
+ThirdParty/
+├─ CommonLibF4/
+├─ xbyak/
+├─ Ultralight-SDK/
+├─ framework-F4-Conversion/
+├─ spdlog/
+└─ tomlplusplus/
+```
+
+### Xbyak
+
+Use Xbyak when the plugin needs low-level hook helpers, runtime assembly generation, trampoline work, or custom patching logic. Xbyak is a header-only x86/x64 JIT assembler library.
+
+```powershell
+git submodule add https://github.com/herumi/xbyak.git ThirdParty/xbyak
+git submodule update --init --recursive
+```
+
+Example `xmake.lua` include:
+
+```lua
+add_includedirs("ThirdParty/xbyak", { public = true })
+```
+
+### Ultralight SDK
+
+Use Ultralight when the mod needs HTML/CSS/JavaScript-driven UI, such as a custom browser, server browser, launcher-like interface, or rich overlay. Ultralight is a GPU-accelerated HTML renderer with C and C++ support.
+
+```powershell
+git submodule add <your-ultralight-sdk-repo-url> ThirdParty/Ultralight-SDK
+git submodule update --init --recursive
+```
+
+Example `xmake.lua` include:
+
+```lua
+add_includedirs("ThirdParty/Ultralight-SDK/include", { public = true })
+```
+
+Linking Ultralight usually requires additional `.lib` files and runtime `.dll` files. Keep those project-specific rather than adding them to the base template.
+
+### framework-F4-Conversion
+
+Use `framework-F4-Conversion` only for mods that depend on NomadsReach's Fallout 4 conversion/UI framework. This should not be required for normal F4SE plugins.
+
+```powershell
+git submodule add https://github.com/NomadsReach/framework-F4-Conversion.git ThirdParty/framework-F4-Conversion
+git submodule update --init --recursive
+```
+
+Example `xmake.lua` include:
+
+```lua
+add_includedirs("ThirdParty/framework-F4-Conversion/include", { public = true })
+```
+
+Only wire this into the build once the mod actually uses it.
+
+### spdlog
+
+Use `spdlog` if the plugin needs more advanced logging than the default template logging setup, such as rotating logs, multiple sinks, custom formatting, or async logging.
+
+```powershell
+git submodule add https://github.com/gabime/spdlog.git ThirdParty/spdlog
+git submodule update --init --recursive
+```
+
+Example `xmake.lua` include:
+
+```lua
+add_includedirs("ThirdParty/spdlog/include", { public = true })
+```
+
+### toml++
+
+Use `toml++` if the plugin needs structured configuration files, for example:
+
+```text
+Data/F4SE/Plugins/MyPlugin.toml
+```
+
+```powershell
+git submodule add https://github.com/marzer/tomlplusplus.git ThirdParty/tomlplusplus
+git submodule update --init --recursive
+```
+
+Example `xmake.lua` include:
+
+```lua
+add_includedirs("ThirdParty/tomlplusplus/include", { public = true })
+```
+
+### SimpleIni
+
+Use SimpleIni for very small `.ini` configuration files. This is useful when the plugin only needs a few basic settings and a TOML parser would be overkill.
+
+```powershell
+git submodule add https://github.com/brofield/simpleini.git ThirdParty/SimpleIni
+git submodule update --init --recursive
+```
+
+Example `xmake.lua` include:
+
+```lua
+add_includedirs("ThirdParty/SimpleIni", { public = true })
+```
+
+### fmt
+
+Use `fmt` if the plugin needs standalone formatting utilities. Some logging libraries already include or depend on `fmt`, so avoid adding it separately unless the project directly needs it.
+
+```powershell
+git submodule add https://github.com/fmtlib/fmt.git ThirdParty/fmt
+git submodule update --init --recursive
+```
+
+Example `xmake.lua` include:
+
+```lua
+add_includedirs("ThirdParty/fmt/include", { public = true })
+```