chore: add Teal/VS Code config, tl check workflow and modding notes

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tlconfig.template.lua

@@ -0,0 +1,11 @@
+return {
+	include_dir = {
+		-- ensure to set proper paths for the definitions for the base game
+		"<tf3_install_folder>api/tealdef",
+		"<tf3_install_folder>base/tealdef",
+
+		-- list your mods here, if you provide your own d.tl definitions
+		-- "example_mod_1",
+	},
+	global_env_def = "all_def"
+}