Add initial implementation for XPL syntax highlighting extension

- Created package.json for the XPL syntax highlighting extension with necessary metadata and dependencies.
- Added syntax definition in xpl.tmLanguage.json to support comments, strings, numbers, tags, and keywords.
- Configured TypeScript compiler options in tsconfig.json for the extension development.

Author: omdxp

.gitignore

@@ -1 +1,5 @@
 /target
+node_modules
+out
+xpl_ls
+*.vsix