DOC: Update title caps validation script to step through directories

[skregas]

Add words that should remain capitalised:

"RangeIndex",
"SparseArray",
"SparseDtype",
"HTTP",
"XML"

Before:
when specifying a directory in the form: doc/source for the script, it would throw an error, because it was looking for only files

After:
can now enter:
script/validate_title_capitalization.py doc/source and it will traverse all the directories below it.

• [X ] related to Fix capitalization among headings in documentation files #32550
• Tests added and passed if fixing a bug or adding a new feature
• [X ] All code checks passed.
• [ X] Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[skregas]

Regarding the checks: 3 are being cancelled. The last one, ci/circleci: test-arm, I don't know why that's failing. I updated my local repo to latest from upstream/main and ran the same test, which passed

[datapythonista]

Instead of this implementation, why you don't simply implement a function that given source_paths yields all the files to check? I think it will be much clearer than what you're doing here. The only change you'd need in this function would be to replace this line by for filename in walk_paths(source_paths):.

Also, please use pathlib instead of os.path.

I don't understand why you skip the png files. If this is to validate rst files, shouldn't we ignore everything that is not rst?

Finally, do you know if this script is being called in the CI? Or why is it not? Are all titles correct after your changes? If that's the case, can you start running it, so we make sure all titles are correct at all times.

I don't think the CI errors are related to your changes, if you update your local branch and push, the CI may become green.

[datapythonista]

@skregas thanks for the work here, do you still want to continue with this PR? There is the comment above that you may want to check if that's the case

[datapythonista]

Closing as stale, but thanks for the work @skregas, and if you eventually want to address the comments, please let me know and I can reopen the PR.