build,Makefile: add 'make mkdocs-serve'

[meowsbits]

This adds a script and associated Makefile command
to handle installing requirements and starting the
development server for mkdocs.

Signed-off-by: meows b5c6@protonmail.com

[ziogaschr]

I wonder if we should add the creation of a virtualenv within the script. As it currently installs the packages globally in the system.

Though not all the developers know/like how to use virtualenvs and at the end a ~/.virtualenv/ dir will be created.

[meowsbits]

Maybe we should just use mkdocs if it's available in the PATH, or exit 1 with some help message about needing to install mkdocs and where to look to do that.

Then we get to have no opinions about Python or environments...

[ziogaschr]

No strong preference on this one. I liked the idea of your script as core-geth is a go project and their users might not know much about python, while most systems have python installed.

[meowsbits]

I'm OK leaving outvirtualenv business. The main reason I had any python management stuff in there was to give context (or an excuse) for putting the python install -r requirements-mkdocs.txt in the code somewhere for sake of documentation. Will push a change to simplify this (and trim responsibility).

EDIT: @ziogaschr Just saw your commit 946fa86 -- LGTM.

[ziogaschr]

Would it make sense adding this in both README and docs? Something across the lines of using MkDocs and here is how to install it and run it locally.

[ziogaschr]

LGTM