[Suggestion] Improve distrobox.ini schema documentation

[Venefilyn]

Is your feature request related to a problem? Please describe.
Currently, looking through the distrobox.ini template and assemble command I'm struck with a sense of when does this execute, what does this mean, how can I do this thing that I want

For example, I want to create a distrobox.ini for a project I'm just starting out in that uses toolbx/distrobox and they have multiple scripts to install things. But pre_init and pre_init_hooks are confusing as to when they execute, what its purpose is etc. And this applies to pretty much every field in the distrobox.ini

Describe the solution you'd like
Distrobox.ini schema is further elaborated on with a clear markdown of what is required, what is optional, and what the different fields do

I should not have to go through source code to figure this out, if anything this should be part of the website and CLI manpage for distrobox-assembly

Describe alternatives you've considered
Maybe we figure out a more standardized approach that could also work for other tools in the future, such as if toolbx decides that a config per-repo would be a good idea we should not use the name distrobox.ini but something like containerbox.ini (this is out of scope for this issue but just wanted to throw it out there)

[89luca89]

Thanks @Venefilyn this was indeed in my todo list

I've explained each option with types and what each one does
let me know if further improvement is needed 👍