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.appdata.xml

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop">
+  <id>org.lite-xl.lite-xl</id>
+  <metadata_license>MIT</metadata_license>
+  <project_license>MIT</project_license>
+  <name>Lite XL</name>
+  <summary>A lightweight text editor written in Lua</summary>
+
+  <description>
+    <p>
+      Lite XL is a text editor and development tool written mainly in Lua,
+      on top of a minimalistic C core using the SDL2 graphics library.
+    </p>
+  </description>
+
+  <screenshots>
+    <screenshot type="default">
+      <caption>The editor window</caption>
+      <image>https://lite-xl.github.io/assets/img/screenshots/editor.png</image>
+    </screenshot>
+  </screenshots>
+
+  <url type="homepage">https://lite-xl.github.io</url>
+
+  <provides>
+    <binary>lite-xl</binary>
+  </provides>
+</component>