Add information on running commands from git bash on windows

[K-Meech]

The commands in the developer docs (+ probably the main docs too) don't work correctly when run from git bash on Windows.
E.g. docker run -v "${PWD}"/data:/data enigma-pd-wml, needs an extra / added before $PWD: docker run -v /"${PWD}"/data:/data enigma-pd-wml

We should add a note on this to the docs for Windows users