Add Apache ProxyPass directive on polyanthum to expose wolpertinger

Over at legacy/trac#32740 (moved), we are developing a new service that will expose a REST API on polyanthum. OONI (and possibly other censorship measurement tools) will query this API to obtain bridges to test.

Please add the following ProxyPass directive to polyanthum's Apache config:

ProxyPass /wolpertinger/ http://127.0.0.1:5000/

(For what it's worth, we've done this before in legacy/trac#30703 (moved), where anarcat documented how he went about implementing this.)