changing fill programatically when generating assets

[itsjavi]

I propose to have a single SVG master file (easier to maintain) and change the fills (light, dark, primary) programatically when generating the assets.

We could use some XML / SVG library for that, or just replace string literals. For the square version we only need to change the first path with a rect.

[mxdvl]

I've got something in the works which should be in a state to share in a day or two…