feat!: introduce petunia

[TorchedSammy]

Petunia is an alternate runner mode for hilbish. the idea is that i don't want hilbish to have this lua-sh fallback hybrid runner anymore, and would like to have something custom and proper which will truly make it hybrid, by making it possible to have both worlds interact together.

more info is at the hyperlink. since this would be an alternate default syntax, it could be considered a breaking change?

additional details:
this is an additional "runner mode" or language in hilbish. this would replace the method of lua fallback sh currently used when interactive. petunia would be designed to be similar to lua but with changes to make it more convenient to use in the context of an interactive shell.

once development starts, it will be made as a native module that can be installed and set as the runner mode. this will allow me to develop it separately and whenever it is finished it will be brought into the source code here.

[erikLundstedt]

would this break support for using fennel instead of lua (me want lispy shell..)?

[TorchedSammy]

runner modes are a feature, this would just be an alternative one (so no)