docs: Clarify custom_templates folder location in options documentation

[KSneijders]

A small PR to (in my opinion) improve the clarity of the custom_templates config option.
The reason for this is that when I read the current line:

the path to a directory containing custom templates. The path is relative to the docs directory

I assumed it meant it was relative to within the docs directory.
Only after looking up other repositories with examples I noticed that you have to include docs in the path if your templates are in that folder.

This is not meant to be final, just an example. If this is not the place for the explanation, I don't mind moving it either.

[pawamoy]

Hi @KSneijders, thank you for your help on improving the docs!

Actually, it seems the custom_templates value is relative to the current working directory, which should be fixed to make it relative to the mkdocs.yml file instead. I'll open a new issue.

[pawamoy]

Can you update this PR to say that the custom templates folder is relative to the current working directory instead of the docs one?

[KSneijders]

Hey @pawamoy!
Thanks for the response! It being relative to the CWD explains a lot.
I've changed the explanation to a simple line without example as the CWD could be different for everyone which makes it difficult to give examples.

[pawamoy]

Thank you for the update, LGTM, merging 🙂