Add GitHubPath

[juftin]

This PR adds an implementation of UPath for fsspec's GithubFileSystem

Resolves #154

[juftin]

There are failing unit tests to address still, a lot of them come down to the fsspec GihubFilesystem being read only (I think 🤔 ). I'll continue to look into them but wanted to get this work out as an example.

[ap--]

Thank you for the PR!

To disable the write tests, you can do it similar to how we handle the http filesystem tests. Just skip the write tests:

universal_pathlib/upath/tests/implementations/test_http.py

Lines 37 to 75 in 7e3836d

	@pytest.mark.skip
	def test_mkdir(self):
	pass
	@pytest.mark.skip
	def test_mkdir_exists_ok_false(self):
	pass
	@pytest.mark.skip
	def test_mkdir_exists_ok_true(self):
	pass
	@pytest.mark.skip
	def test_mkdir_parents_true_exists_ok_true(self):
	pass
	@pytest.mark.skip
	def test_mkdir_parents_true_exists_ok_false(self):
	pass
	@pytest.mark.skip
	def test_makedirs_exist_ok_true(self):
	pass
	@pytest.mark.skip
	def test_makedirs_exist_ok_false(self):
	pass
	@pytest.mark.skip
	def test_touch_unlink(self):
	pass
	@pytest.mark.skip
	def test_write_bytes(self, pathlib_base):
	pass
	@pytest.mark.skip
	def test_write_text(self, pathlib_base):
	pass

[ap--]

Hmm and regarding the file access tests:

I wonder if we should add the test files to this repo, so that the base tests can be identical.

maybe under upath/tests/data/

[ap--]

I took your PR and ported it to the newer UPath implementation here: 8314a65

Thanks again for your contribution 🙏 ❤️