install: fix firefox install

Also actually add it to the completions and valid modules

completions/caelestia.fish

@@ -22,7 +22,7 @@ complete -c caelestia -n $not_seen -a 'wallpaper' -d 'Change the wallpaper'
 complete -c caelestia -n $not_seen -a 'pip' -d 'Picture in picture utilities'
 
 # Install
-set -l commands all discord fish foot fuzzel hypr safeeyes scripts shell gtk vscode
+set -l commands all discord firefox fish foot fuzzel hypr safeeyes scripts shell gtk vscode
 complete -c caelestia -n "$seen install && not $seen $commands" -a "$commands"
 
 # Shell

install/firefox.fish

@@ -21,7 +21,13 @@ end
 # Install zen css
 if test -d $HOME/.zen
     for profile in $HOME/.zen/*/chrome
-        cp $dist/zen.css $profile/userChrome.css
+        for file in userChrome userContent
+            if test -f $profile/$file.css
+                echo -e "@import url('$dist/zen/$file.css');\n$(cat $profile/$file.css)" > $profile/$file.css
+            else
+                echo "@import url('$dist/zen/$file.css');" > $profile/$file.css
+            end
+        end
     end
 end
 

main.fish

@@ -35,7 +35,7 @@ if test "$argv[1]" = scheme
 end
 
 if test "$argv[1]" = install
-    set -l valid_modules scripts discord fish foot fuzzel hypr safeeyes shell gtk vscode
+    set -l valid_modules scripts discord firefox fish foot fuzzel hypr safeeyes shell gtk vscode
     if test "$argv[2]" = all
         for module in $valid_modules
             $src/install/$module.fish $argv[3..]