Improve automatic indentation in Gleam code files (#8098)

Release Notes:

- Improved automatic indentation in Gleam code files
([#7295](https://github.com/zed-industries/zed/issues/7295)).

crates/zed/src/languages/gleam/indents.scm

@@ -1 +1,3 @@
+(_ "[" "]" @end) @indent
 (_ "{" "}" @end) @indent
+(_ "(" ")" @end) @indent