This PR adds basic runnable tests for Gleam.
Functions with names ending in `_test` will be available for running:
https://github.com/zed-industries/zed/assets/1486634/9f3f81e5-a7fa-425c-a5a2-d615062486bb
Release Notes:
- N/A
@@ -0,0 +1,6 @@
+; Functions with names ending in `_test`.
+; This matches the standalone test style used by Startest and Gleeunit.
+(
+ (function name: (_) @run
+ (#match? @run ".*_test$"))
+) @gleam-test