Release notes for nushell 0.71

[sholderbach]

Please add your important new features and breaking changes to the release notes by commiting to/opening a PR against the release-notes-0.71 branch! Thanks for helping out!

[sholderbach]

@fdncred @merelymyself @PerBothner @webbedspace @rgwood
I saw that you made some user facing changes that might be worth talking about in the release notes. Feel free to fill in the sections with a few short sentences or a good code example. If you don't have time the team will probably still be able to fill in the blanks (with maybe a less perfect example)

@dandavison do we need to document things about the change to the completion logic (for users that take the new default config or those that run the old default config)?

[PerBothner]

If you're OK with a plug for DomTerm, how about the following? If you want I can also add a screenshot.

How nushell outputs values can now be customized via display_output hook (PerBothner)

This new (somewhat experimental) hook is useful for modifying how values are printed or diverting the output to a different window. This could be an IDE or "notebook" interface that can handle "rich output" such as HTML.
See this section of the book.

A motivating example was to use inline HTML in the DomTerm terminal emulator.

    if "DOMTERM" in (env).name {{
        display_output: { to html --partial --no-color | domterm hcat  }
    }} else {{ }}

[PerBothner]

If you feel a screenshot would be good, please add the following after my previous comment:

The screenshot shows the output from the du and ls Make* commands. (The first table is mostly scrolled out, but the the header is shifted so as to keep it visible.)

[dandavison]

I'm not sure I'm going to have time to write a section on completion unfortunately :/

[webbedspace]

Add this:
"
Because lists are so important in Nushell, adding an operator for joining them (similar to Python's +) was deemed acceptable. This was implemented as a separate operator, ++, and not implemented as an overload of + because + is currently used for addition of same-typed values in two series (a dataframe datatype representing same-typed lists).

Note: Currently, this operator cannot be used to join two tables (which are, of course, lists of records). This functionality is still being worked on and will likely be present in the next version.
"

[webbedspace]

Add this:
"
Formerly, merge's type signature only accepted, as an argument, blocks returning records instead of just plain records. This restriction, which conflicted with append's signature, has now been lifted. It is also likely that, due to the fact that little expressive power is gained from having merge accept blocks returning records, that that part of its type signature will be removed in a future version.
"

[webbedspace]

Hasn't the "hope to have more information for you soon" line been in the past several release notes? What does it refer to? The 0.80 draft roadmap?