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.

xmake.lua

@@ -0,0 +1,37 @@
+-- F4SEPluginTemplate
+-- Minimal reusable Fallout 4 F4SE plugin template using CommonLibF4.
+
+includes("ThirdParty/CommonLibF4")
+
+set_project("F4SEPluginTemplate")
+set_version("0.1.0")
+set_license("MIT")
+set_languages("c++23")
+set_warnings("allextra")
+
+add_rules("mode.debug", "mode.releasedbg")
+add_rules("plugin.vsxmake.autoupdate")
+
+target("F4SEPluginTemplate")
+    add_rules("commonlibf4.plugin", {
+        name = "F4SEPluginTemplate",
+        author = "YourName",
+        description = "Fallout 4 F4SE plugin template using CommonLibF4"
+    })
+
+    add_files("src/**.cpp")
+    add_headerfiles("src/**.h")
+    add_headerfiles("include/**.h")
+    add_includedirs("src", "include")
+    set_pcxxheader("src/pch.h")
+
+    after_build(function (target)
+        local outdir = path.join(os.projectdir(), "package", "F4SE", "Plugins")
+        os.mkdir(outdir)
+        os.cp(target:targetfile(), outdir)
+
+        local pdb = path.join(target:targetdir(), target:basename() .. ".pdb")
+        if os.isfile(pdb) then
+            os.cp(pdb, outdir)
+        end
+    end)