[add] github actions and some vim version in test

[get-me-power]

Hello, cocopon. Thanks for creating great Vim plugin. I add github-actions.

• This removes the circleci's dependency.
• Add more vim version in test e.g: vim8.1, vim8.2...

Could you check this PR? If you don't need this pull request, feel free to close it.

reference

https://github.com/kazukazuinaina/vaffle.vim/pull/1/checks?check_run_id=798523891

https://github.com/thinca/action-setup-vim

[get-me-power]

This CI may run if you merge this patch in master...

[get-me-power]

@cocopon If you don't need this, feel free to close it.

[cocopon]

Great! Sorry for my late reply and thank you for your contribution.

[get-me-power]

@cocopon Thanks for your review and merge!