Dark theme for fileshelter

Installation instructions when using DEB package:

1. Clone this repo into /opt/FileShelter_Dark
2. Symlink fileshelter-dark.css file into the file css folder of the fileshelter docroot
3. Add @import "fileshelter-dark.css"; to the top off fileshelter.css the same folder, this will tell it to load the theme css file

Install commands when using DEB package:

#Clone repo
git clone https://git.bprieshof.nl/DarkTheme/FileShelter_Dark /opt/FileShelter_Dark
# Symlink file into place
ln -s /opt/FileShelter_Dark/fileshelter-dark.css /usr/share/fileshelter/docroot/css/fileshelter-dark.css
# Enable theme by prepending an import to fileshelter.css (this should also be run everytime Fileshelter is updated)
sed -i '1i@import "fileshelter-dark.css";' /usr/share/fileshelter/docroot/css/fileshelter.css