Implement RTD support

[MicahGale]

Pull Request Checklist for MontePy

Description

This sets up the configuration for RTD, and tweaks the theme to work better with RTD. This:

• Adds support for ethical ads
• Adds "MontePy" to navbar
• Switches to / to support multi-version
  • will set an RTD redirect for migration plan to keep deprecation warnings valid
• Added meta descriptions to most top level pages.
• Added support for Epub and PDF

Fixes #593, Fixes #594

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Post Merge Checklist

• configure idaholab/montepy on RTD
• setup webhooks/ GHA to test build
• verify links and sitemaps
• Switch to stable as default.
• Migrate domain to RTD
• Remove github pages from metadata

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General Checklist

• I have performed a self-review of my own code.
• The code follows the standards outlined in the development documentation.
• I have added tests that prove my fix is effective or that my feature works (if applicable).
• I have made corresponding changes to the documentation, providing clear details on the added or modified functionality (if applicable).

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Documentation Checklist

• I have documented all added classes and methods.
• For infrastructure updates, I have updated the developer's guide.
• For significant new features, I have added a section to the getting started guide.

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First-Time Contributor Checklist

• If this is your first contribution, add yourself to pyproject.toml if you wish to do so.

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Additional Notes for Reviewers

Ensure that:

• The submitted code is consistent with the merge checklist outlined here.
• The tests pass locally before CI checks.
• The PR covers all relevant aspects according to the development guidelines.
  """

[MicahGale]

Sitemaps are no longer needed. RTD handles that: https://docs.readthedocs.io/en/stable/reference/sitemaps.html

[MicahGale]

Demo: https://pers-montepy.readthedocs.io/en/latest/

[MicahGale]

https://montepy.readthedocs.io/en/latest/