(cherry picked from commit d54a37a51b16fb6e46093265d65fd47d5318f67f)

Co-authored-by: Jack Koenig <koenig@sifive.com>

(cherry picked from commit 68510515467ef7a86c54b2e710bfc5e736f7a2aa)

Co-authored-by: Gonsolo <gonsolo@gmail.com>

This new document is a place to describe issues users may run into when
upgrading from Chisel 3.4 to 3.5. This initial version includes the
solution for the removal of virtual method "val io".

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

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

* Update experimental-features.md

Added title to Experimental features

* Update experimental-features.md

* Update docs/src/appendix/experimental-features.md

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

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

This PR provides for support for Vec literals. They can be one of two forms
Inferred:
```
Vec.Lit(0x1.U, 0x2.U)
```
or explicit:
```
Vec(2, UInt(4.W)).Lit(0 -> 0x1.U, 1 -> 0x2.U)
```
- Explicit form allows for partial, or sparse, literals.
- Vec literals can be used as Register initializers
- Arbitrary nesting (consistent with type constraints is allowed)

* Add documentation guide about memory initialization

* Move information to experimental and add ref

* Update the FAQ and add doc on versioning
* Update modules.md

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

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