Add version control file icon for gitcommit files (#21935)

Closes: https://github.com/zed-industries/zed/issues/21734

<img width="976" alt="SCR-20241212-nlci"
src="https://github.com/user-attachments/assets/d567e2c8-d803-4148-b159-ae781eb59b50"
/>

I added the same file extensions that are used in the `Git Firefly`
extension.


b521b71324/languages/gitcommit/config.toml (L5-L9)

Release Notes:

- Added version control file icon for gitcommit files.

assets/icons/file_icons/file_types.json

@@ -59,6 +59,11 @@
     "gitignore": "vcs",
     "gitkeep": "vcs",
     "gitmodules": "vcs",
+    "TAG_EDITMSG": "vcs",
+    "MERGE_MSG": "vcs",
+    "COMMIT_EDITMSG": "vcs",
+    "NOTES_EDITMSG": "vcs",
+    "EDIT_DESCRIPTION": "vcs",
     "gleam": "gleam",
     "go": "go",
     "gql": "graphql",