Add Electron apps to how to contribute

[bilelmoussaoui]

We should add a small paragraph on how to get the icons from the asar.file

[andia89]

Hmm. I don't know. It is actually pretty hard to figure out the right icons, isn't it?

[bilelmoussaoui]

Yes, the hardest part is finding the key of the icons :( but we can just explain briefly how that works and how to extract an asar file using asar npm package, what do you think?

[bilelmoussaoui]

Added few texts, can you see if everything is cristal clear?

[andia89]

Looks fine 👍