✨ Remove Rich tags when showing completion text

[svlandeg]

Upon completion, print the help text with Rich if it's available. Fixes #822.

Original behaviour, as reported in #822: hitting TAB TAB shows the autocompletion with literal Rich formatting, e.g.

goodbye -- Say [bold]goodbye[/bold] to the user.

With this PR, the Rich tags are removed:

goodbye -- Say goodbye to the user.

In my experiments, this does not yet actually format the text with the right colors etc. Not sure whether that's due to the shells/OS's I've tried - further input from others using different systems would be appreciated!

Powershell on Windows

• Shows Rich tags in completion text with master
• Removes Rich tags in completion text with this PR
• Shell is able to show Rich formatting in simple script
• Shows Rich formatting in completion text with this PR

GitBash using zsh shell on Windows

I couldn't yet get this shell to work with Rich formatting - probably because it's an emulated shell.

• Shows Rich tags in completion text with master
• Removes Rich tags in completion text with this PR
• Shell is able to show Rich formatting in simple script
• Shows Rich formatting in completion text with this PR

[kinuax]

PR Review according to #821.

zsh on Linux

• Shows Rich tags in completion text with master
• Removes Rich tags in completion text with this PR
• Shell is able to show Rich formatting in simple script
• Shows Rich formatting in completion text with this PR