Improve docs

[James-Mart]

Content changes

• I deleted the docs that describe how to generate wildcard certs with certbot, and use nginx/godaddy. Those instructions were too specific and could become outdated if those third-parties change and therefore they are outside the scope of our docs. I added a more general replacement in run-infrastructure/configuration/https.md.
• Rewrote much of the introduction page (/README.md), which was generally outdated and not very well written.
• Added a brief page describing the intent of the AccountNumbers object (/development/format/account-numbers.md)

Structural changes

• Eliminated all of the manual tables of contents, and added a table-of-contents plugin that adds TOC to the right hand side of the docs (in desktop view).
• Reorganized the entire book into categories that I think make more sense. There's a lot more work to be done in this category, but this is a start.
• Reorganized the structure of the book to have README.md inside each section, which is the convention used by the mdbook docs themselves. Makes it easier to locate the intro page for each section.

Mdbook changes

• Updated the version of mermaid used by the mdbook-mermaid crate by dynamically loading the mermaid library instead of bundling it with the book. The version bundled with mdbook-mermaid is old.
• The docs now support the "edit on github" button, which will link to the correct page on which edits are being made.
• Turned on mdbook-linkcheck by default to detect at build time if anyone breaks links in the docs
• Turned off the "print" button, which didn't work well for our book anyway with mermaid diagrams, etc.

Further notes

• Lots of links don't have a corresponding page yet, I don't plan to resolve all missing pages in this PR.

[James-Mart]

Eliminated the doc on app interfaces, which I will add in a separate PR

[swatanabe]

I know I'm in a minority, but I like being able to view documentation offline...

[James-Mart]

You can, your penalty is just that you will have to deal with a text representation of the mermaid diagram 😜

[swatanabe]

The layout has a few issues (depending on the window size)

• The vertical next button can cover the page TOC making it hard to use it to navigate
• The size and position of the TOC don't seem to match, as the right side can overflow the window

[James-Mart]

• The next/previous buttons have been hidden. Not very useful controls anyways.

• The TOC is hidden on smaller resolution screens, and the docs look good on at least the following devices with known resolutions:
  

The only real issue is on desktops where the resolution is unusual or the window is not maximized. I think this won't affect many people and can be fixed later.