make mako config templateable

config/mako/update_theme.sh

@@ -2,19 +2,10 @@
 
 . "${HOME}/.cache/wal/colors.sh"
 
-conffile="${HOME}/.config/mako/config"
+export background_color="${background}89"
+export text_color="$foreground"
+export border_color="$color13"
 
-# Associative array, color name -> color code.
-declare -A colors
-colors=(
-    ["background-color"]="${background}89"
-    ["text-color"]="$foreground"
-    ["border-color"]="$color13"
-)
-
-for color_name in "${!colors[@]}"; do
-  # replace first occurance of each color in config file
-  sed -i "0,/^$color_name.*/{s//$color_name=${colors[$color_name]}/}" $conffile
-done
+envsubst <$HOME/.config/mako/config.template >$HOME/.config/mako/config
 
 makoctl reload