Remove templates

[cknitt]

As mentioned by @cristianoc here: #5678 (comment), templates are very outdated and should probably be dropped altogether.

Also, I just noticed that you need to run scripts/pack.js after changing a template. This is actually documented in jscomp/bsb/Docs.md, but nobody would read that if it's not in the CONTRIBUTING.md.

The templates will then be packed into bsb_templates.ml and thereby in rescript.ml, unnecessarily increasing the size of rescript.exe.

[cristianoc]

The command-line option should also be removed, together with the resulting dead code.

[fhammerschmidt]

That's sad. Although I never used templates other than the default one, I keep a global installation of ReScript to be able to quickly generate projects for repro's, etc. with rescript init.

[cknitt]

Such functionality should be decoupled from the compiler IMHO.

Maybe we could have something like https://github.com/mahezsh/create-rescript-app?

[johnridesabike]

Decoupling from the compiler could also possibly enable using npm init, eliminating the need for a global ReScript installation.

[DZakh]

I've started working on a decoupled script. I had a problem with the previous rescript init that it poorly works in existing js codebases. I'd like to improve this.