[hotfix] Add a docs page with module specific guides for flink contributors

[slinkydeveloper]

What is the purpose of the change

This PR adds a new page to add module specific guides for flink contributors.

Brief change log

• Added the new module specific guides doc page
• Added how to debug the sql planner guide

Verifying this change

This change is only docs

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[Airblader]

There seems to be some overlap with https://flink.apache.org/contributing/code-style-and-quality-components.html with this?

[flinkbot]

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Automated Checks

Last check on commit 7593fde (Tue Sep 28 09:13:25 UTC 2021)

Warnings:

• Documentation files were touched, but no docs/content.zh/ files: Update Chinese documentation or file Jira ticket.

_{Mention the bot in a comment to re-run the automated checks.}

Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

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[slinkydeveloper]

@Airblader yep it seems like, perhaps I can modify the page you linked to be more "generic", and not specific to code style? Or do you have something else in mind?

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CI report:

• 7593fde Azure: SUCCESS

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[slinkydeveloper]

Moved to apache/flink-web#480