Add script and job to trigger a docs build

What does this MR do?

Manually trigger a docs build so that you can preview any docs changes live.

Test cases

• The docs project doesn't have the branch created. The manual action should: 1) create the remote branch, 2) trigger the pipeline on that branch
• The docs project already has the branch. That means you've already built the docs preview once, made changes in the MR and want to deploy again. The manual action should: 1) skip the creation of the remote branch, 2) trigger the pipeline on that branch
• If the remote branch creation or trigger fail for some reason, the job fails with a descriptive message.
• When the MR is merged and the branch is deleted, a manual stop job is run which deletes the remote branch and in turn another manual stop job is triggered where it cleans up the deployed app.
• Manual builds works for forks also.