Release notes for 0.84.0 (#988)

* Release notes for `0.84.0`

Please add your new features and breaking changes to the release notes
by opening PRs against the `release-notes-0.84.0` branch.

* add the breaking changes (from 2023-07-26)

* add the full changelog (from 2023-07-26)

* do not include changes before the 0.83.1 patch release

this commit basically recomputes the breaking changes and the
full changelog from 2023-07-30 instead of 2023-07-26.

* add the raw list of all PRs

* remove the ones that occured before 0.83.1

* split the most interesting PRs in proto-sections

* write the shoutout section

this commit also moves two PRs
- one to *The standard library*
- the other one to *Scripting*

* update the full changelog

* Update full changelog to current state

I had to pass `2023-07-29` to get the full range of commits

* Update breaking changes based on label

* Table images

* Add export const and scope notes (#1011)

* Add intro sentence; Change `str replace` note (#1012)

* Add section on table and `format` commands

* Small tweaks

* Update 2023-08-22-nushell_0_84_0.md

Add PR author

* Break down shoutouts to separate sections (#1013)

* Sections for release notes (#1014)

* Sections for `http` and `dfr`

* Start a section with curated bugfixes

* Breaking change note

* Finish up release notes

* fix typos

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Co-authored-by: Stefan Holderbach <[email protected]>
Co-authored-by: Jakub Žádník <[email protected]>