Add SteamOS GPU fixes and launch script

Introduces SteamOS/Steam Deck detection and GPU configuration in gpu-config.js, adds a dedicated start-steamos.sh launch script, and updates package.json with new scripts for SteamOS and Linux GPU-safe launches. Also adds a comprehensive GPU troubleshooting guide in GPU-FIX-README.md to address rendering issues on various platforms.

start-steamos.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+# SteamOS/Steam Deck launch script for Nebula Browser
+# This script applies necessary flags for proper rendering on SteamOS/Gamescope
+
+# Detect if running on SteamOS
+if [ -f /etc/steamos-release ] || [ -f /usr/share/steamos/steamos.conf ]; then
+    echo "SteamOS detected"
+fi
+
+# Detect if running under Gamescope (Steam Deck's compositor)
+if [ -n "$GAMESCOPE_WAYLAND_DISPLAY" ] || [ -n "$SteamDeck" ]; then
+    echo "Gamescope/Steam Deck environment detected"
+fi
+
+# Get the directory where this script is located
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# Launch Nebula with SteamOS-compatible flags
+# These flags help with webview rendering issues on AMD GPUs under Gamescope
+exec electron "$SCRIPT_DIR" \
+    --ozone-platform=x11 \
+    --disable-gpu-compositing \
+    --disable-gpu-vsync \
+    --disable-accelerated-2d-canvas \
+    --use-gl=desktop \
+    --no-sandbox \
+    --disable-dev-shm-usage \
+    --disable-gpu-sandbox \
+    --disable-features=VizDisplayCompositor \
+    --enable-unsafe-swiftshader \
+    "$@"