Add a manual documenting config file options

[H-Shay]

This is the first step to fixing #8159. Once this documentation is approved, I can move forward with pulling out all the redundant documentation from the configuration file itself.

A few things:
-For the most part the description of each config setting is pulled directly from the comments in the original document, I tried not change it too much, most of the changes I made were to add context or to clarify the documentation in a different context. If you see anything that is unclear please flag it and I can change it.
-The document is huge. It probably makes sense to have people only review a section at a time (there is an index of sections at the beginning of the file). If you review a section, please note in the comment section below which section you looked at, so others don't duplicate your work.
-I've been staring at this document for far too long and I am sure I have missed spelling/grammar errors or urls which should be converted to links. Please keep an eye out for them!

[babolivier]

That's some impressive work, thanks Shay!

Some drive-by comments having a very quick look at it:

• I think it'd be very useful to be able to link to specific configuration settings, so maybe consider making their names titles
• the page needs to be added to SUMMARY.md so it can appear on the configuration website

(plus the two I've added on the diff)

[richvdh]

this is fantastic, thank you so much!

[anoadragon453]

I would love the ability to be able to link to specific config options, rather than only section headers. To do this, we'd need to create a header for each config option, something like:

#### Config option: `log_config`

While this works, it unfortunately will result in adding every config option to the table of contents sidebar, which makes it less useful.

Creating a method of marking headers in our documentation as "do not add this to the table of contents" would be worthwhile in a few cases, and something I can add to the table of contents code. We could then later apply it to this document to allow granular linking.

[H-Shay]

I would love the ability to be able to link to specific config options, rather than only section headers. To do this, we'd need to create a header for each config option, something like:

#### Config option: `log_config`

While this works, it unfortunately will result in adding every config option to the table of contents sidebar, which makes it less useful.

Creating a method of marking headers in our documentation as "do not add this to the table of contents" would be worthwhile in a few cases, and something I can add to the table of contents code. We could then later apply it to this document to allow granular linking.

Would something like adding a custom html tag to each option be an acceptable solution? I.e.:

<h7>Config option: `server_name`</h7>

The tags aren't visible when it's rendered, but linking still works (I built the book locally to verify that), and we could add a little line in here that says something like "skip me if I'm an H7"?