Enhancements

Add support for adding proxy provider to custom group in Clash configurations.
Add and, or, bool as template function.
Add support for any amount of argument for template function join.
inja: Add variadic function callback support.

base/pref.ini

@@ -181,6 +181,7 @@ surge_ruleset=!!import:snippets/rulesets.txt
 
 ;custom_proxy_group=g1hk`select`!!GROUPID=0!!(HGC|HKBN|PCCW|HKT|hk|港)
 ;custom_proxy_group=sstw`select`!!GROUP=V2RayProvider!!(深台|彰化|新北|台|tw)
+;custom_proxy_group=provider`select`!!PROVIDER=prov1,prov2,prov3`fallback_nodes
 
 ;Also supports using script for filtering nodes. A "filter" function with one argument which is an array of all available nodes should be defined in the script.
 ;custom_proxy_group=script`select`script:/path/to/script.js