Fix manifest keys const name error in PR #27 (#29)

* fix manifest keys const not being renamed in a previous commit

Author: ithinkandicode

loader/mod_loader.gd

@@ -49,8 +49,7 @@ const UNPACKED_DIR = "res://mods-unpacked/"
 const REQUIRED_MOD_FILES = ["mod_main.gd", "manifest.json"]
 
 # Required keys in a mod's manifest.json file
-const REQUIRED_META_TAGS = [
-	"id",
+const REQUIRED_MANIFEST_KEYS_ROOT = [
 	"name",
 	"version_number",
 	"website_url",