Default to github.token

[nuhkoca]

To simplify the action, we can add the github.token in the default field for the repo-token input. This would make the action a bit less verbose for normal use. Now the action will default to github.token without needing an explicit definition.

Note: I don't know how to test this properly so that it'd be good if you can test whether or not it works as expected.

[MichaelDeBoey]

Duplicate of #227

[MaksimZhukov]

Hello @nuhkoca! Thank you for the contribution! We have already merged these changes (#227)and published new release (v4.0.3).