Update readme badges

[imciner2]

Add new GitHub actions badge, remove Travis/Appveyor badgers, update URL for code coverage badge.

[coveralls]

Pull Request Test Coverage Report for Build 918990191

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

---

Totals
Change from base Build 918859679:	0.0%
Covered Lines:	87
Relevant Lines:	87

---

💛 - Coveralls