Updates to chisel3 documentation for website:
* guard code examples with mdoc and fix errors encountered along the way
* move some website content here vs splitting the content across two repos
* Bring in the interval-types and loading memories content so that it will be visible from the website
* remove all references to the wiki (deprecated)
* Remove reference to Wiki from the README
* fix tabbing and compile of chisel3-vs-chisel2 section
* Appendix: faqs now guarded and compile
* FAQs: move to resources section

* Fix some botched formatting (replace ```mdoc scala with ```scala mdoc)
* Replace some unnecessary uses of triple backticks with single
  backticks
* Move appendix docs from wiki-deprecated/ to appendix/
  * This will require an update on the website as well
* Update Bundle literal docs

Co-authored-by: Megan Wachs <megan@sifive.com>

* Fix crosslinks in mdoc. Can't use md suffix

* Removed all .md crossrefs

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Causes issues when building the website, using these docs.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

* Fix broken mdoc

* Added test-chisel-docs to ci workflow

* Add requirement on build-treadle job

* Added forgotton colon

* Forgot cd into chisel3 dir

* moved three docs into explanations

* Updated reference

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@gmail.com>