We should investigate using GitHub actions to allow us to test against Windows and macOS platforms in addition to the existing Linux tests on Travis.

Checklist for replacing Travis:

• Tests on Linux (Multi Platform CI Pipeline with GitHub Actions #651)
• Tests on macOS (Multi Platform CI Pipeline with GitHub Actions #651)
• Tests on Windows (Multi Platform CI Pipeline with GitHub Actions #651)
• Linting (Multi Platform CI Pipeline with GitHub Actions #651)
• Docs (Move more Travis jobs to GitHub Actions #705)
• Typechecking (Move more Travis jobs to GitHub Actions #705)
• Deploy/release (Move more Travis jobs to GitHub Actions #709; see Replace Travis with GitHub Actions #650 (comment) and Replace Travis with GitHub Actions #650 (comment))