yamllint: Lint more YAML extensions

Match YAML files with any ending and exclude extension which are known
to break yamllint. For example, *.erb, *.gz, *.bz2.

The following files are checked additionally:
- ./config/secrets.yml.example
- ./config/database.yml.postgresql
- ./config/resque.yml.example
- ./config/cable.yml.example
- ./config/gitlab.yml.example
- ./config/database.yml.decomposed-postgresql
- ./config/sidekiq.yml.example
- ./.solargraph.yml.example