### What changes were proposed in this pull request?
This PR proposes to add getting started- installation to new PySpark docs.
### Why are the changes needed?
Better documentation.
### Does this PR introduce _any_ user-facing change?
No. Documentation only.
### How was this patch tested?
Generating documents locally.
Closes#29640 from rohitmishr1484/SPARK-32180-Getting-Started-Installation.
Authored-by: Rohit.Mishra <rohit.mishra@utopusinsights.com>
Signed-off-by: Sean Owen <srowen@gmail.com>
