Release notes for nushell 0.78 (#830)

* Release notes for `0.78`

Please add your new features and breaking changes to the release notes
by opening PRs against the `release-notes-0.78` branch.

* Document optional cell path members

* Add placeholders

* Mention empty list changes

* Mention comparison operator breaking change

* add a note about better `error make` (#849)

* Update 2023-04-04-nushell_0_78.md

* Update 2023-04-04-nushell_0_78.md

* Update 2023-04-04-nushell_0_78.md

* Update 2023-04-04-nushell_0_78.md

* Update 2023-04-04-nushell_0_78.md

* Update 2023-04-04-nushell_0_78.md

* Mention added `math exp`

* Update 2023-04-04-nushell_0_78.md

* Expand alias changes

* add #8366 to the release notes (#848)

* add #8366 to the release note

* make the title more explicit for the reader

* be more explicit about what "pretty format" means

* fix nuon quoting

* Update 2023-04-04-nushell_0_78.md

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Co-authored-by: Reilly Wood <[email protected]>
Co-authored-by: Antoine Stevan <[email protected]>
Co-authored-by: JT <[email protected]>
Co-authored-by: Jakub Žádník <[email protected]>

Author: 5 people