Commit template and $EDITOR support

[noirbizarre]

A colleague of mine shared with me 2 easy possible improvements for cz commit I want to share for feedback before submitting pull-requests.

git commit --template

Currently, committers have the choice between a fully prompted approach using cz commit and no assistance except a pre-commit check.

He suggested that commitizen provide git commit --template <tpl> support, so people used to commit from their editors would just have a commit template generated from the plugin.

I think this is a good idea and could take the form of a simple flag cz commit --template which would basically wraps git commit --template <path/to/commitizen-generated.template> with a commit template generated from the plugin prompts.

$EDITOR support for multiline prompts

The discussion with him started by this. He asked me if cz commit has some kind of support for opening multiline prompts into $EDITOR.

I took a look at questionnary and prompt-toolkit which are used behind the scene, and there is
a open_in_editor method allowing that.

I imagine we can add a flag --editor to cz commit to open multiline prompts in the editor.

What do you think ?