Add GH action to replace Travis CI

[nomiddlename]

Travis CI stopped working for open source builds a long time ago. This PR adds a github action to do the build.

[lamweili]

1. CI on Windows is failing because it didn't reach 100% coverage, namely due to the exclusion below:
   

   streamroller/test/RollingFileStream-test.js

   Lines 415 to 419 in 17731e1

   	// in windows, you can't delete a directory if there is an open file handle
   	if (process.platform !== "win32") {
   	describe("when the directory gets deleted", function() {
   	var stream;

2. Not exactly sure why CI on Windows will sometimes cancel themselves.

3. The fs.ensureDir (instead of fs.ensureFile) is deliberate (since 17731e1) for RollingFileWriteStream.js:267 test coverage. Maybe should add a comment.
   

   streamroller/test/RollingFileWriteStream-test.js

   Lines 1422 to 1424 in 19e2181

   	before(done => {
   	fs.ensureDir(path.join(__dirname, "tmp-delete-test/logfile.log.2"), done);
   	});

   
   

   streamroller/lib/RollingFileWriteStream.js

   Lines 264 to 269 in 17731e1

   	const deleteFiles = fileNames => {
   	debug(`deleteFiles: files to delete: ${fileNames}`);
   	return Promise.all(fileNames.map(f => fs.unlink(f).catch((e) => {
   	debug(`deleteFiles: error when unlinking ${f}, ignoring. Error was ${e}`);
   	})));
   	};