git-commit: highlight statuses according to length

This is simpler than the neovim counterpart, we simply switch
scope based on length:

* 1-50: `markup.heading`
* 51-72: `warning`
* 73+: `error`

closes helix-editor#2882

runtime/queries/git-commit/highlights.scm

@@ -1,4 +1,9 @@
-(subject) @markup.heading
+((subject) @markup.heading
+ (#match? @markup.heading "^.{1,50}$"))
+((subject) @warning
+ (#match? @warning "^.{51,72}$"))
+(subject) @error
+
 (path) @string.special.path
 (branch) @string.special.symbol
 (commit) @constant