closes#5160
## Summary / motivation (required)
This PR fixes typos, misspelings and (in one place) formatting in files
under `docs-site/` and one file under `docs/`.
I've found these using `codespell` and `typos` CLI utilities (+ spotted
a few myself).
## Scope
- [x] This PR is focused on one change (no unrelated edits).
***
Note: I've installed mdbook following the updated installation steps
(a4d6fb39a7),
but now i face a new error:
```rust
$ mdbook build
2026-07-15 14:48:28 [ERROR] (mdbook::utils): Error: Couldn't open SUMMARY.md in "/home/user/anki-source/docs-site/src" directory
2026-07-15 14:48:28 [ERROR] (mdbook::utils): Caused By: No such file or directory (os error 2)
```
I don't have time right now to figure out what is the difference between
`ankitects/anki-manual` and `ankitects/anki` directory structure and how
to merge them to make the mdbook build, but *I think that my changes are
trivial enough* that no thorough testing is needed.
Co-authored-by: Abdo <abdo@abdnh.net>
625eefdd42