languages: add highlighting for go.mod (#7137)

Release Notes:

- Added syntax highlighting for go.mod files. Fixes #7133 

<img width="863" alt="image"
src="https://github.com/zed-industries/zed/assets/8725798/dc521a02-c53a-44aa-b0c1-eebf31835679">
ba91adf48aDerrick Laird committed on 1/31/2024, 7:46:13 AM· committed by GitHubparente5fe811
7 files changedLine totals unavailable