Add GPG auto-sign commands

[sih4sing5hong5]

Why:

Add automatic signing commands in docs.

Relative issues:

• https://github.com/github/docs/issues/18218#issuecomment-1137336102
• https://github.com/github/docs/pull/15311

What's being changed (if available, include any code snippets, screenshots, or gifs):

Thank for amazing preview

This commands is in sixth steps:

Check off the following:

• [x] I have reviewed my changes in staging (look for the "Automatically generated comment" and click the links in the "Preview" column to view your latest changes).
• [x] For content changes, I have completed the self-review checklist.

[welcome[bot]]

Thanks for opening this pull request! A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[github-actions[bot]]

Automatically generated comment ℹ️

This comment is automatically generated and will be overwritten every time changes are committed to this branch.

The table contains an overview of files in the content directory that have been changed in this pull request. It's provided to make it easy to review your changes on the staging site. Please note that changes to the data directory will not show up in this table.

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Content directory changes

You may find it useful to copy this table into the pull request summary. There you can edit it to share links to important articles or changes and to give a high-level overview of how the changes in your pull request support the overall goals of the pull request.

Source	Preview	Production	What Changed
authentication/managing-commit-signature-verification/telling-git-about-your-signing-key.md	fpt ghec ghes@ 3.6 3.5 3.4 3.3 3.2 ghae	fpt ghec ghes@ 3.6 3.5 3.4 3.3 3.2 ghae

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fpt: Free, Pro, Team ghec: GitHub Enterprise Cloud ghes: GitHub Enterprise Server ghae: GitHub AE

[sih4sing5hong5]

It seems Link Checker was broken.

Run node .github/actions/rendered-content-link-checker.js
  node .github/actions/rendered-content-link-checker.js
  shell: /usr/bin/bash -e {0}
  env:
    LEVEL: critical
    ACTION_RUN_URL: https://github.com/github/docs/actions/runs/3286389283
    GITHUB_TOKEN: 
    SHOULD_COMMENT: true
    CHECK_EXTERNAL_LINKS: false
    CREATE_REPORT: false
file:///home/runner/work/docs/docs/.github/actions/lib/get-env-inputs.js:13
        throw new Error(`You must supply a ${envVarName} environment variable`)
              ^

Error: You must supply a GITHUB_TOKEN environment variable
    at file:///home/runner/work/docs/docs/.github/actions/lib/get-env-inputs.js:13:15
    at Array.map (<anonymous>)
    at getEnvInputs (file:///home/runner/work/docs/docs/.github/actions/lib/get-env-inputs.js:10:13)
    at file:///home/runner/work/docs/docs/.github/actions/rendered-content-link-checker.js:55:3
Error: Process completed with exit code 1.

[cmwilson21]

@sih4sing5hong5 Thanks so much for opening a PR! I'll get this triaged for review :zap:

[github-actions[bot]]

Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours. If you're looking for your next contribution, check out our help wanted issues :zap:

[sih4sing5hong5]

Hi @sih4sing5hong5, thanks for raising the PR sparkles This looks like a worthwhile addition. Have just added a little bit of information to the step to add some clarity slightly_smiling_face

@isaacmbrown Thanks. It's more user-friendly!! :+1: