Inject custom user styles into all frames
Inject custom user styles into all frames

This fixes #2594.

smblott-github/vimium,poacher2k/vimium,poacher2k/vimium,gdh1995/vimium,philc/vimium,smblott-github/vimium,decaffeinate-examples/vimium,mrmr1993/vimium,smblott-github/vimium,philc/vimium,gdh1995/vimium,decaffeinate-examples/vimium,philc/vimium,mrmr1993/vimium,decaffeinate-examples/vimium,poacher2k/vimium,mrmr1993/vimium,gdh1995/vimium