[SPARK-33003][PYTHON][DOCS] Add type hints guidelines to the documentation

[zero323]

What changes were proposed in this pull request?

Add type hints guidelines to developer docs.

Why are the changes needed?

Since it is a new and still somewhat evolving feature, we should provided clear guidelines for potential contributors.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

[SparkQA]

Test build #130022 has finished for PR 30094 at commit 6928aa4.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Kubernetes integration test starting
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[SparkQA]

Kubernetes integration test status success
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[HyukjinKwon]

Looks pretty good. Let me know when you think it's ready @zero323

[SparkQA]

Test build #130109 has finished for PR 30094 at commit 88a04a7.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Kubernetes integration test starting
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/34718/

[SparkQA]

Kubernetes integration test status failure
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/34718/

[zero323]

Thanks for checking this @HyukjinKwon! I think it is ready for review ‒ I've modified grammar as requested and section about validating.

As of user part, I decided against adding it for now. I have some hints, but these seem to be too localized (specific editors, common typing issues), while for most of the users, benefits will be mostly transparent. Maybe we could add a short guide for different environments (I have this answer on Stack, which seems to be weirdly popular) and add some typing notes there?

[HyukjinKwon]

LGTM

[HyukjinKwon]

Merged to master.

[zero323]

Thanks @HyukjinKwon!