Add documentation section to README

[alok-kumar0421]

This PR adds a simple Documentation section to the README.
The repository did not have a dedicated place that pointed new users or contributors to the
right resources, so I added a short section with links and basic guidance.

The intention is to make the README a little more helpful for anyone trying to understand
where to find important information related to Kvrocks.

If anything needs to be improved or adjusted, I can update it.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.06%. Comparing base (6c56470) to head (73dd1d3).
⚠️ Report is 102 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable     #368      +/-   ##
============================================
+ Coverage     43.38%   49.06%   +5.67%     
============================================
  Files            37       45       +8     
  Lines          2971     3783     +812     
============================================
+ Hits           1289     1856     +567     
- Misses         1544     1719     +175     
- Partials        138      208      +70     

Flag	Coverage Δ
unittests	49.06% <ø> (+5.67%)	⬆️

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[alok-kumar0421]

Thank you for reviewing and merging my PR!

I would like to continue contributing to Kvrocks Controller.
If there are any areas where help is needed or any issues you recommend for me, please let me know.
I’m happy to work on more tasks and improve the project further.

[git-hulk]

@alok-kumar0421 Thanks for your interest. You could have a look at the issues list: https://github.com/apache/kvrocks-controller/issues.

[alok-kumar0421]

Thanks for the guidance! I’ll go through the issues list and pick one to start working on.
If I have any questions while exploring, I’ll reach out.