Add github action for broken link check in connectors element templates

[ztefanie]

Description

This PR is related to this issue: https://github.com/camunda/team-connectors/issues/889
The solution suggested is a monthly running job, checking with docusaurus build for incorrect links inside the element templates of connectors.

An issue created by this looks like this: #4995

When should this change go live?

• This is a bug fix, security concern, or something that needs urgent release support. (add bug or support label)
• This is already available but undocumented and should be released within a week. (add available & undocumented label)
• This is on a specific schedule and the assignee will coordinate a release with the DevEx team. (create draft PR and/or add hold label)
• This is part of a scheduled alpha or minor. (add alpha or minor label)
• There is no urgency with this change (add low prio label)

PR Checklist

• My changes are for an upcoming minor release and:
  • are in the /docs directory (version 8.8).
  • are in the /versioned_docs/version-8.7/ directory (version 8.7).
• My changes are for an already released minor and are in a /versioned_docs directory.

• I added a DRI, team, or delegate as a reviewer for technical accuracy and grammar/style:
  • Engineering team review
  • Technical writer review via @camunda/tech-writers unless working with an embedded writer.

[github-actions]

👋 🤖 ✅ Looks like the changes were ported across versions, nice job! 🎉

You can read more about the versioning within our docs in our documentation guidelines.

[sbuettner]

@ztefanie Please check this comment before merging this here: https://github.com/camunda/team-connectors/issues/889#issuecomment-2659404853

[pepopowitz]

I have multiple concerns about accepting this PR. Among them: (1) It seems like a lot of complexity for the docs to take on for changes that will be occurring in the connectors repo (if I'm understanding the workflow correctly); (2) We already have multiple versions of link-checking, and I'd like to see if we can make one of them work before introducing another.

I'd like to talk about this PR in person. I'm going to send a calendar invite to @akeller, @ztefanie, @sbuettner, and @mesellings to discuss.

[pepopowitz]

As discussed in person, we're going to take a different approach on this, summarized below:

1. @ztefanie will push up a PR with a new file similar to productlinks.txt, containing links referenced by connector templates.
2. I will confirm that the product link validation is functioning properly for both anchors & redirects
3. I will alter our CI workflows to validate links in the new file
4. 🎉