Use global switch to enable/disable preview images

.env.dev.example

@@ -52,3 +52,15 @@ EMAIL_USE_SSL=false
 
 # Set this to true when initializing certbot for domain, false when not
 CERTBOT_INIT=false
+
+# Preview image generation can be computing and storage intensive
+# ENABLE_PREVIEW_IMAGES=True
+
+# Specify RGB tuple or RGB hex strings,
+# or use_dominant_color_light / use_dominant_color_dark
+PREVIEW_BG_COLOR=use_dominant_color_light
+# Change to #FFF if you use use_dominant_color_dark
+PREVIEW_TEXT_COLOR=#363636
+PREVIEW_IMG_WIDTH=1200
+PREVIEW_IMG_HEIGHT=630
+PREVIEW_DEFAULT_COVER_COLOR=#002549