* clang-tidy action: Exclude lib & tests dir for clang-tidy CI checks
The lib dir is obvious, but the tests dir is disabled because gtest has
a million different thing that clang-tidy doesn't like, while they're in
reality perfectly reasonable
* clang-tidy-action: Disable the LGTM comment
* ci: format yaml and json files with prettier
* chore: add changelog entry
* fix: format everything
* ci: run pretter on all files
* ci: rename prettier step
