[skip changelog] Add task and workflow to check for dead links in docs

[silvanocerza]

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Adds a task and a workflow to verify that links in the documentations are still working.

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See how to contribute

[silvanocerza]

Markdown links checks are failing cause of this:

FILE: ./docs/CONTRIBUTING.md
[✖] https://github.com/arduino/arduino-cli/deployments?environment=github-pages#activity-log

ERROR: 1 dead links found!

18 links checked.
[✖] https://github.com/arduino/arduino-cli/deployments?environment=github-pages#activity-log → Status: 404

That link is not visible by everyone, should we remove it or find another solution?

[per1234]

Thanks Silvano! This is really great.

18 links checked.
[✖] https://github.com/arduino/arduino-cli/deployments?environment=github-pages#activity-log → Status: 404

should we remove it or find another solution?

I recommend removing it. Even for the few who have the required permissions and will visit that link, I don't think it adds much value. For all the other contributors, the 404 link is only a waste of time.

I looked for general documentation from GitHub on this subject, but I didn't find anything that is directly relevant to the deployment to GitHub Pages (it's all about deployments in general).

[per1234]

What is the reason for using the fetch-depth: 0 setting?

[silvanocerza]

fetch-depth: 0 fetches the whole history, branches and tags. Should have been set at 1 really, there's no need to fetch everything, I'll change it.