erlang_ls: Look for lib includes in extra_deps

This fixes ErlangLS include lookups for `include_lib` attributes like

```erl
-include_lib("khepri/lib/include.hrl").
```

when running erlang_ls and building with Bazel.

`khepri` ends up in the `extra_deps` directory as a symlink after
running `bazel run //tools:symlink_deps_for_erlang_ls`, so this change
picks up that `khepri` directory as a lib for `include_lib`s.

(cherry picked from commit df827452f7)

erlang_ls.config

@@ -17,6 +17,7 @@ diagnostics:
 include_dirs:
   - "deps"
   - "deps/*/include"
+  - "extra_deps"
   - "extra_deps/*/include"
 lenses:
   enabled: