#96 and #101: Documentation updates: Implementation Guide, Releases, and Roadmap

[brendanreardon]

This Pull Request contains changes to documentation related Issues #101: Add Decision Record and Product Roadmap into readthedocs and #96: Add Reference implementation to docs. Additional changes were made to align with style presented in VRS' readthedocs. Photos of documentation pages are included as comments on this Pull Request.

Specifically,

• The info box was removed from the Appendices page, because it was a note for a to do.
• The FAQ page was removed from appendices because it only references the Discussions on GitHub and the Getting Involved pages.
• The Product Roadmap was added to the appendix, @DanielPuthawala migrated most of the Google Doc already in Pull Request 145.
• The design decisions page was renamed from Cat-VRS Roadmap to Product Roadmap.
• The Getting Involved page was revised with editorial changes.
• The Implementation Guide was revised to give a high level overview of how to get started with cat-vrs, as well as include a hyperlink to the reference implementation. The analogous page on VRS' readthedocs is the Quick Start page, which refers users to the VRS Python notebooks. Each concept in the VRS documentation includes an example and implementation guidance, and I think that it would be nice to revise our documentation to be like this too (good job VRS!). Perhaps this would be a good strategy for GKS products broadly.
• The Releases page was revised to align with how it is presented within VRS' documentation.

Added labels to a few pages so that they can be referenced. Specifically: appendices, data model, how cat-vrs works, and introduction.

Pull Request checklist:

• Does the title of this Pull Request reference the corresponding Issue?
• Is the branch validating against pre-commit hooks? Run pre-commit run --all-files from the root directory.
• Is the branch passing tests? Run pytest tests/ from the root directory.

The schema was not contributed to in this Pull Request.

[brendanreardon]

Revision to Design Decisions page:

[brendanreardon]

Revised Appendix index page:

[brendanreardon]

Product roadmap page, previously not exposed within the documentation.

[brendanreardon]

Minor changes to Getting Involved:

[brendanreardon]

Revised Implementation Guide:

[brendanreardon]

Releases page, aligned with VRS' Releases page.

[brendanreardon]

p.s. I believe that I am breaking contribution guidelines by addressing more than one open Issue with this Pull Request 🙈 Sorry!