Updated Meson configuration

- Added version and license metadata
- Configuration data to be used in configured files to set metadata
- Portable binary and directories in the main install directory
- Binary file installed in correct places for all supported platforms
- Freedesktop AppStream support
- Added missing files install rules

resources/linux/org.lite-xl.lite-xl.desktop

@@ -0,0 +1,10 @@
+[Desktop Entry]
+Type=Application
+Name=Lite XL
+Comment=A lightweight text editor written in Lua
+Exec=lite-xl %F
+Icon=lite-xl
+Terminal=false
+StartupNotify=false
+Categories=Utility;TextEditor;Development;
+MimeType=text/plain;