[SPARK-46116][DOCS][PYTHON] Adding "Stack Overflow" and "Mailing List…

…s" link into PySpark doc homepage

### What changes were proposed in this pull request?

This PR proposes to enhance the PySpark documentation by adding more items for a "Useful links"including "Stack Overflow", "Dev Mailing List" and the "User Mailing List".

### Why are the changes needed?

It is aimed at improving user engagement and providing quick access to community support and discussions. This approach is inspired by the [Pandas documentation](https://pandas.pydata.org/docs/index.html), which effectively uses a similar section for community engagement.

The "Stack Overflow" will lead users to a curated list of StackOverflow questions tagged with `pyspark`, while the mailing lists will offer platforms for deeper discussions and insights within the Spark community.

### Does this PR introduce _any_ user-facing change?

No API change, but the main page of the PySpark documentation will be updated to include a new "Useful links"as below:

<img width="1197" alt="Screenshot 2023-11-27 at 5 29 19 PM" src="https://github.com/apache/spark/assets/44108233/0d52e243-8e97-4a5b-9dc9-ecb941496b10">

## Linked pages for each items

### Stack Overflow

<img width="935" alt="Screenshot 2023-11-27 at 2 59 31 PM" src="https://github.com/apache/spark/assets/44108233/78deff80-ccc8-4969-9966-cb308ba2a71d">

### Dev Mailing List
<img width="1601" alt="Screenshot 2023-11-27 at 3 00 23 PM" src="https://github.com/apache/spark/assets/44108233/64b70a59-8120-47a7-94f4-4a4a6fe94e69">

### User Mailing List
<img width="1604" alt="Screenshot 2023-11-27 at 3 00 44 PM" src="https://github.com/apache/spark/assets/44108233/af77ef5d-c594-448d-ba7e-63d89d6e176c">

### How was this patch tested?

Manually build doc & verify each links.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #44033 from itholic/improve_useful_links.

Authored-by: Haejoon Lee <[email protected]>
Signed-off-by: Kent Yao <[email protected]>

python/docs/source/index.rst

@@ -24,7 +24,7 @@ PySpark Overview
 **Date**: |today| **Version**: |release|
 
 **Useful links**:
-|binder|_ | `GitHub <https://github.com/apache/spark>`_ | `Issues <https://issues.apache.org/jira/projects/SPARK/issues>`_ | |examples|_ | `Community <https://spark.apache.org/community.html>`_
+|binder|_ | `GitHub <https://github.com/apache/spark>`_ | `Issues <https://issues.apache.org/jira/projects/SPARK/issues>`_ | |examples|_ | `Community <https://spark.apache.org/community.html>`_ | `Stack Overflow <https://stackoverflow.com/questions/tagged/pyspark>`_ | `Dev Mailing List <https://lists.apache.org/[email protected]>`_ | `User Mailing List <https://lists.apache.org/[email protected]>`_
 
 PySpark is the Python API for Apache Spark. It enables you to perform real-time,
 large-scale data processing in a distributed environment using Python. It also provides a PySpark