Xontrib-sh

What's Changed
* Fixed issue where xonsh returns string representation of shell list by psuedomagi in https://github.com/anki-code/xontrib-sh/pull/10

New Contributors
* psuedomagi made their first contribution in https://github.com/anki-code/xontrib-sh/pull/10

**Full Changelog**: https://github.com/anki-code/xontrib-sh/compare/0.3.0...0.3.1

Added `cmd`, `pwsh` support. Thanks eugenesvk !

Fixes. Thanks to eugenesvk!

Now you can can set the shell name explicitly i.e. `!bash ` or `!b ` (the first letter of the shell). Thanks to eugenesvk!

Compiled python.

* Now you should type space after exclamation point. It's to avoid collisions with `!<str>` from bashisms.
* Added syntax errors printing if appropriate shell not determined.
* Removed additional print to avoid duplication prompt printing