finish the documentation (!198)

this is an attempt at finishing the documentation for real.

the convention is
- start sentences with capital letter, speaks as 3rd person and end with period
- specify non-trivial cases and returns in the doc, otherwise, leave that to the tests
- use mathematical formulae to make things more clear

>  **Note**
>
> might supersede !184

For now, i completely skipped FRI because i thought we could do that in a later MR, as it was added later and is not even part of a public release yet.

I also went a bit faster on _aPlonK_ as it is so complex and we will likely never use it.

## changelog
> -  is for documentation changes
> -  is for code changes

- () moves the `RUSTDOCFLAGS` for Katex activation to `.cargo/config.toml`
- () adds `simple_mermaid` for Mermaid graphs
- () upgrades Katex from `0.10.0` to `0.16.21` for matrix support
- documentation
  - [x] () () `algebra`: check the length for `algebra::powers_of`
  - [x] () () `algebra::linalg`: use exact matches in the error tests and use struct errors
  - [x] () () `error`: change some errors to struct errors
  - [x] () () `fs`: rename some arguments, e.g. `block_hashes` to `hashes` and `dump_dir` to `directory`
  - [x] () () `zk`: inline `check_degree_is_too_large`
  - [x] ()          `fec`
  - [x] ()          `semi_avid`
  - [x] ()          `kzg`
  - [x] () () `aplonk`: remove `Commitment` and `VerifierKey`
  - [ ] ()          `fri`
  - [x] ()          Komodo (`lib.rs`)