Add env-var for image-name and manual dispatch to build workflow

[Wuodan]

These are some small changes to allow

• overriding the image-name in forks github action settings for tests
• trigggering the "Deploy" workflow manually in GitHub for tests

My other PRs will include these 2 base commits, you or others may find them useful too.

Background:
Seeing that OpenHands uses one of these images as base image, I originally wanted to use these images for project aicage as base-image and for a util-image.
But I ended up not using python-nodejs mainly because I wanted a latest tag and this was missing for arm64.
My PRs here are merely things for image-building in GitHub workflow which I couild easily transfer back from project aicage.

[nikolaik]

Thanks for all your PRs Stefan <3

Made a few stylistic comments on this one

[Wuodan]

Thank you for this open source repo!

I updated this PR #373 and merged the changes into the other 2 PRs #375 and #377 with a small fix in #375.

Test-runs:

PR	Branch	GH Action Run	Image Repository
#373	upstream-PR/00-workflow-test-nobs	23243561023	wuodan/python-nodejs_pr00
#375	upstream-PR/02-replace-qemu-with-arm64-runner	23243601563	wuodan/python-nodejs_pr02
#377	upstream-PR/04-fix-latest-tag-missing-for-arm64	23243613553	wuodan/python-nodejs_pr04

• Failures in the final job Update versions.json and README.md are due to running the action with non-main branch.
  It works with main branch (example action-run).
• Durations of the above GH Action Runs are not representative as all ran in parallel and there is a limit of max. 20 parallel jobs per GitHub repo.
• In my tests with QEMU a full run takes ~30min while with arm64 GH runners it takes ~20min.

Run 23243601563 needed a restart with "Re-run failed jobs" because one job was canceled with error:

##[error]The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.

GH actions are not fully reliable, I've seen such random failures or network problems before.