* Release notes for `0.86`

Please add your new features and breaking changes to the release notes
by opening PRs against the `release-notes-0.86` branch.

## TODO
- [ ] look at interesting contributions
- [ ] write all the sections
- [ ] order the sections by interest
- [ ] add the breaking changes
- [ ] detail the breaking changes
- [ ] add the full changelog

* add sections we use these days + note on "warning" banner

* add all the contributions in a raw table

this commit does not list the ones from dependabot.

* remove the dependency updates

* add a section for bug fixes

* add a section about the type system

* add a section about changes to commands

* add a section about our platform support

* add a section about better errors

* add a section about internal changes

* add a section about the documentation

* add a section about completions

* add a section for the standard library

* write the "hall of fame"

* write the "type system" section

* complete the "hall of fame"

this adds "platform support" and "better errors" to it.

* add TODOs for remaining sections

* make a real note at the top

* add TODOs for the excerpt

* write the "completions" section

* write the section about the standard library

* coreutils cp introduction

* write the "commands" section

* move the paragraph about uutils to "commands" section

* add missing most recent contributions

* write notes about the last contributions in raw table

a bunch of them were bug fixes in the end and have been put in the "bug
fixes" section accordingly.

* add a table of content

* add the breaking changes

* add the full changelog

* update full changelog

* move sections, add summary

* breaking change details

* typo

* Extend notes about bool options and def changes (#1109)

---------

Co-authored-by: Darren Schroeder <343840+fdncred@users.noreply.github.com>
Co-authored-by: JT <547158+jntrnr@users.noreply.github.com>
Co-authored-by: Jakub Žádník <kubouch@gmail.com>