Add support to stream output from Github Actions

[tmc]

The problem I'm trying to solve: Add support to stream output from Github Actions

How I imagine hub could expose this functionality: hub actions logs -f <RUN_ID>

[moul]

For curious people, here is an example of what it may look like if the log stream API would be easily available: https://github.com/moul/git-ci/

I managed to make this PoC by using a browser cookie (which is difficult to document and bad in term of security)