Drop appveyor in favor of native Github Actions

[Ash258]

After Shovel stable release 0.6

1. [ ] Move to organization
2. [ ] Drop linux branches
3. [ ] Adopt main branch
4. [ ] Switch from Appveyor
   • https://github.com/Ash258/GithubActionsBucketForTesting/blob/main/.github/workflows/ci.yml
   1. [ ] Check dependencies caching
   2. [ ] Optimize

https://pipelines.actions.githubusercontent.com/cA0CTE0w1Ui1KaBfW7EzhuUa6DnFcXPjHuZqVzCpODOTt1NjMK/_apis/pipelines/1/runs/15449/signedlogcontent/3?urlExpires=2021-04-02T14%3A32%3A00.2281961Z&urlSigningMethod=HMACV1&urlSignature=8xPajD8Xpd83pXa%2BDQwV7%2Fd26ST6K2jFGaflUFYkNtM%3D