Add jgmenu, chaiNNer, workrave & droidcam icons

Tried my hand at making some icons and put them in the ./apps/scalable folder. They should be automatically assigned as I matched their names with their hicolor equivalents 😄

Previews:

chaiNNer

jgmenu

workrave

Hope you like these! I tried my best to conform with the style of the amazing existing icons. If there's any changes or optimisations you'd like me to make, please let me know ^^ I'm quite new to Inkscape so please pardon my noobiness.