Upgraded the documentation to use the latest docfx tool

[paulushub]

[!NOTE] For the documentation review, I have deployed the output to GitHub-Pages on my fork. URL: https://paulushub.github.io/SVG/

Nerdbank.GitVersioning is currently generating error in docs build, probably because it is building on my fork!

Description

• Updated the builddocs.yml to the new docfx workflow format.
• Renamed the doc to Docs
• Moved the doc/*.md files to Docs/articles/*.md
• Moved the docfx.json to Docs/docfx.json (updated to support latest docfx version)
• Moved the index.md to Docs/index.md

Type of change

• [x] Documentation changes, no change in main source codes (non-breaking change which fixes an issue)
• [x] This change does not require a documentation update
• [x] A Docs/Readme.md file, to be included as Readme file in NuGet Package.
• [x] Update revision notes
• [ ] Resolved review issues.

How Has This Been Tested?

• [x] Docfx builds locally with a warning (can be ignored), due to the generator.

[mrbean-bremen]

Off-topic: this PR is actually not relevant for a patch release, and may still take a while to get finally consolidated. Would it be ok if I made a patch release without it (see #1147)?

[mrbean-bremen]

Re: typos - we probably need a type checker hook to make this easier - I use this in my Python repos... It is easy to overlook typos.

As for the patch release - I'll probably just do it - releases are cheap!

[mrbean-bremen]

I'm going to merge this now, as all problems seem to be resolved (I updated the copyright in the last commit). If more changes are needed, we can make new PRs.