Add a link checker into CI

[erogluorhan]

Closes #1395

Overview

Adds a link checker into the CI workflow.

Also fix a broken URL in one of the notebooks.

PR Checklist

General

• An issue is linked created and linked
• Add appropriate labels
• Filled out Overview

[review-notebook-app]

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[rajeeja]

I worry the timeout of 60 min is too long?

[erogluorhan]

I worry the timeout of 60 min is too long?

Yeah, maybe. Since it was going to involve docs generation, I wanted to be safe, but now I reduced it to 15 mins. Let's see how it will go with that, and then we can make a decision.

[erogluorhan]

I worry the timeout of 60 min is too long?

Yeah, maybe. Since it was going to involve docs generation, I wanted to be safe, but now I reduced it to 15 mins. Let's see how it will go with that, and then we can make a decision.

@rajeeja

Currently, it takes slightly less than 15 mins; hence, I set it to 20 mins for now.

Also, link checker finds two 404s for the time being, but that is because the UXarray docs pages those URLs were attempting to point were never generated (user API entries for ball tree and kd-tree). This PR added those two entries, so once it is merged, those broken links are expected to be fixed since pages will be live. We will need to approve with them (if there is no other issue with this PR)

Feel free to give a review.

[rajeeja]

The change is the great! Thank you so much!