fix: add lua to languages contribution points

This commit adds the missing entry for the `lua` language to the
languages contribution points (`contributes.languages` field) in the
extension manifest (`package.json`).

Author: IronGeek

package.json

@@ -3235,6 +3235,15 @@
 			}
 		],
 		"languages": [
+			{
+				"id": "lua",
+				"extensions": [
+					".lua"
+				],
+				"aliases": [
+					"Lua"
+				]
+			},
 			{
 				"filenames": [
 					".luarc.json",