Trusted publishing GitHub Action docs should specify `environment` if there is one about guides

[woodruffw]

Just flagging: I'll send a PR for the environment docs part later today, time permitting.

[woodruffw]

For context: the equivalent docs on the PyPI side: https://docs.pypi.org/trusted-publishers/using-a-publisher/

Specifically, this is the example we use on PyPI:

jobs:
  pypi-publish:
    name: upload release to PyPI
    runs-on: ubuntu-latest
    # Specifying a GitHub environment is optional, but strongly encouraged
    environment: release
    permissions:
      # IMPORTANT: this permission is mandatory for trusted publishing
      id-token: write
    steps:
      # retrieve your distributions here

      - name: Publish package distributions to PyPI
        uses: pypa/gh-action-pypi-publish@release/v1

This can be closely adapted to RubyGems, so I'll file a PR later today.

[mschwager]

It's probably also worth mentioning that the release-gem GitHub Action requires that your project be using rake-release. Unfortunately, that doesn't really work for my intended workflow because rake-release performs a git tag and git push when releasing. I'd like for my release process to be triggered on git tag, so rake-release then creates an unnecessary tag. I also received this error from release-gem when it attempted to create the tag:

Tagged v0.5.0.
fatal: You are not currently on a branch.
To push the history leading to the current (detached HEAD)
state now, use

    git push origin HEAD:<name-of-remote-branch>

Untagging v0.5.0 due to error.
rake aborted!
Running `["git", "push", "--quiet"]` failed, exit code: 128

All in all, it'd be nice if release-gem could do a simple gem build -> gem push.

EDIT: some additional context: rubygems/release-gem#3.

[woodruffw]

"Later today" really meant a week, but I've opened #356 for this!