Replace Travis CI with GitHub action

[jaylinski]

This change replaces the broken Travis CI with a new GitHub action.

Also all outdated Node.js versions were removed. Only maintained Node.js versions are tested now.

https://nodejs.org/en/about/releases/

Related to #1671.

• Please don't start pull requests for security issues. Instead, file a report at https://www.npmjs.com/advisories/report?package=handlebars
• Maintain the existing code style
• Are focused on a single change (i.e. avoid large refactoring or style adjustments in untouched code if not the primary goal of the pull request)
• Have good commit messages
• Have tests
• Have the typings (lib/handlebars.d.ts) updated on every API change. If you need help, updating those, please mention that in the PR description.
• Don't significantly decrease the current code coverage (see coverage/lcov-report/index.html)
• Currently, the 4.x-branch contains the latest version. Please target that branch in the PR.