Add support for executing recipes in vterm

[skissue]

As proposed in #54.

I just went ahead and chose v and V as the keybinds since they made sense to me, but I'm open to changing it if desired. RIght now the keys are always bound and then vterm's presence is checked when the commands are called (via require); I'm not sure if this is the best way to support this as an "optional" feature, so I'm open to feedback on that as well.

[psibi]

How about introducing a new defcustom instead ? Something like justl-default-shell with two choices: eshell and vterm. eshell can be the default.

The advantage that is that there is no need to introduce new keybinding. Based on the option configured, you use the existing keybinding.

[skissue]

I went ahead and changed it to use the justl-shell option, which defaults to eshell, and converted justl-exec-eshell into a generic justl-exec-shell function. I'm not sure if the code is the cleanest it could be 😅, but everything seems to be working for me.

Additionally, I'm wondering whether an obsolete alias should be added for justl-exec-eshell, since the function has been renamed 🤔.

[psibi]

Actually, I liked your previous implementation even though it will likely add more code. Can you do the following:

• Define new function justl-exec-vterm and justl-no-exec-vterm similar to how you did before.
• Create new function justl-exec-shell and justl-no-exec-shell as you have defined in the latest commit. This function should call the apprpriate functions based on the justl-default-shell variable.

The main motivation is to make it easier to add support for other shells.

[skissue]

• Define new function justl-exec-vterm and justl-no-exec-vterm similar to how you did before.

Done.

• Create new function justl-exec-shell and justl-no-exec-shell as you have defined in the latest commit. This function should call the apprpriate functions based on the justl-default-shell variable.

Done. I updated the default keybinds to use these functions.

The main motivation is to make it easier to add support for other shells.

I agree that this is a better approach to accomplish this goal.

Let me know if there are any other changes you'd like me to make.

[psibi]

Thank you!