Update instructions for devs

[tbentham]

More detail/context in general, for example:

-How to install certain tools, what they're needed for. -How to run a local server. -Current instructions seem tailored to Linux and back end devs, so need more detail for Windows and front end (even if just to say "you don't need to install this").

Just examples - interpret as you see fit.

Impact

High

Urgency

Now

[jamesgeddes]

@SamWinterhalder demoted, please prioritise PGL tasks