https://github.com/slimsag/vscode-bazel/tree/patch-1/syntaxes

Following https://github.com/sourcegraph/syntect_server#adding-languages

Add to file_extensions:

```
- build_defs
- BUILD.in
```

(see https://github.com/bazelbuild/vscode-bazel/pull/195#discussion_r417920624 and https://github.com/sourcegraph/sourcegraph/pull/18666)
