Disable icon downloads, accept optional query after icon href, format and clippy fixes

.env.template

@@ -43,6 +43,12 @@
 ## It's recommended to also set 'ROCKET_CLI_COLORS=off'
 # LOG_FILE=/path/to/log
 
+## Disable icon downloading
+## Set to true to disable icon downloading, this would still serve icons from $ICON_CACHE_FOLDER,
+## but it won't produce any external network request. Needs to set $ICON_CACHE_TTL to 0,
+## otherwise it will delete them and they won't be downloaded again.
+# DISABLE_ICON_DOWNLOAD=false
+
 ## Controls if new users can register
 # SIGNUPS_ALLOWED=true