add editable install instructions for bqt devs

[hannesdelbeke]

for development purpose, we currently symlink a repo to the correct location in blender modules or addons folder. so any changes auto affect blender, without need to reinstall bqt or copy folders over.

however symlink sometimes causes some bugs, where files might be deleted if i uninstall the addon. and if i hadnt commited these files, they are gone forever.

editable pip install should be a cleaner approach similar to symlinking, with .pth file cleanly linking this. but haven't gotten this to work yet in Blender. think it might be related to the fact that .pth files only work in site packages folder, and blender doenst use these.

investigate

Original symlink instructions When working on the bqt code from a repo, to prevent having to reinstall bqt every time you make a change, you can symlink the bqt folder to your blender addons folder to develop bqt. Any updates in the repo are then reflected in blender on restart. e.g.: mklink /J "C:\Users\USERNAME\AppData\Roaming\Blender Foundation\Blender\2.93\scripts\addons\bqt" "C:\Users\hanne\OneDrive\Documents\repos\_Blender\bqt\bqt"

[hannesdelbeke]

TODO: add to wiki https://github.com/techartorg/bqt/wiki

[hannesdelbeke]

added to https://github.com/techartorg/bqt/wiki/setup-bqt-develop-environment