feat(publisher-gcs): implemented Google Cloud Storage publisher

[mahnunchik]

Implemented Google Cloud Storage publisher (GCS)

ISSUES CLOSED: #1751

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

Implemented Google Cloud Storage publisher based on official library https://github.com/googleapis/nodejs-storage

[malept]

Are you volunteering to maintain this publisher? There are already a lot of publisher modules in this monorepo without a maintainer and I'd like to avoid more.

Alternatively, you can also maintain this in a separate repository.

[mahnunchik]

@malept yep, why not. It is pretty simple and I'm interested in this publisher.

[malept]

I've added you as a code owner of this module via GitHub's CODEOWNERS feature. You'll get pull request notifications any time files in the publisher module get changed.

Can you please add a pull request in https://github.com/MarshallOfSound/electron-forge-docs (which powers electronforge.io) for this module?

[mahnunchik]

Code fixed, documentation added ✅

[malept]

This is blocked until I get access to merge PRs in the docs repo.

[mahnunchik]

Ok, got it.

@MarshallOfSound could you please look into electron-forge/electron-forge-docs#9

[mahnunchik]

@malept Hi, I think electron-forge/electron-forge-docs#9 can be merged.

[mahnunchik]

@malept What should I do to have this PR merged?

[mahnunchik]

@malept PR is rebased on latest master in new PR #2100