Add some files that belong in every repo.
- `.editorconfig` is based on `gitea` repo.
- `.gitattributes` is useful for Windows users.
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/186
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: delvh <dev.lh@web.de>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>