Fix the styling for advanced-setting on Firefox
Fix the styling for advanced-setting on Firefox

On Firefox, the advanced-setting textarea was not filling the whole
space, this adds height: 100% to it to fix that issue.

Fixes #1798

MinFu/uproxy,dhkong88/uproxy,chinarustin/uproxy,dhkong88/uproxy,roceys/uproxy,uProxy/uproxy,uProxy/uproxy,jpevarnek/uproxy,jpevarnek/uproxy,jpevarnek/uproxy,chinarustin/uproxy,roceys/uproxy,qida/uproxy,roceys/uproxy,qida/uproxy,itplanes/uproxy,qida/uproxy,jpevarnek/uproxy,dhkong88/uproxy,dhkong88/uproxy,dhkong88/uproxy,itplanes/uproxy,MinFu/uproxy,qida/uproxy,uProxy/uproxy,roceys/uproxy,chinarustin/uproxy,MinFu/uproxy,itplanes/uproxy,itplanes/uproxy,jpevarnek/uproxy,MinFu/uproxy,uProxy/uproxy,itplanes/uproxy,chinarustin/uproxy,roceys/uproxy,uProxy/uproxy,qida/uproxy,chinarustin/uproxy,MinFu/uproxy