Provide short git.checkout_submodules doc line

[Bedzior]

Hi!

I realised there's a missing line of documentation for a neat function in the Git helper tool.

Basically, I was looking for the most straightforward way to checkout submodules after a shallow clone. Luckily enough my IDE pointed me to checkout_submodules, which does the submodule checkout only, without duplicating checkout for root repository (as checkout would).

I would be happy to see this accepted, unless I am doing something horribly wrong, in which case I am open to criticism.

R.

[CLAassistant]

All committers have signed the CLA.

[Bedzior]

If any other part of the documentation could see an update to showcase shallow cloning to a wider audience, please let me know!

[memsharded]

Sorry this was never reviewed or managed. Unfortunately, this Git tool has been superseded by from conan.tools.scm import Git new one, so these docs are no longer necessary. Thanks!