feat: add microsoft pptx file converter

[jlonge4]

Proposed Changes:

Adding microsoft pptx converter to convert slides to text.

How did you test it?

Manual verification

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 6971610642

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
To ensure accuracy in future PRs, please see these guidelines.
A quick fix for this PR: rebase it; your next report should be accurate.

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.07%) to 40.223%

---

Files with Coverage Reduction	New Missed Lines	%
nodes/file_converter/init.py	1	88.89%

Totals
Change from base Build 6971133323:	0.07%
Covered Lines:	10688
Relevant Lines:	26572

---

💛 - Coveralls

[anakin87]

It seems good!

I see some small opportunities for improvements
(I added suggestions.)

[anakin87]

Wow, very good!

Once the tests pass, I will merge it...

Thanks for your 1st Haystack contribution 🥳 🎈

[jlonge4]

@anakin87 changes committed, thanks so much for all of your patience man, as well as the improvements! Thanks to you perhaps my next one will go much more smoothly lol