make thumbnails compatible with dirkeys/filekeys

was intentionally skipped to avoid complexity but enough people have
asked why it doesn't work that it's time to do something about it

turns out it wasn't that bad

tests/util.py

@@ -43,6 +43,7 @@ if MACOS:
 
 from copyparty.__init__ import E
 from copyparty.__main__ import init_E
+from copyparty.ico import Ico
 from copyparty.u2idx import U2idx
 from copyparty.util import FHC, CachedDict, Garda, Unrecv
 
@@ -161,6 +162,7 @@ class Cfg(Namespace):
             s_wr_sz=256 * 1024,
             sort="href",
             srch_hits=99999,
+            th_covers=["folder.png"],
             th_crop="y",
             th_size="320x256",
             th_x3="n",
@@ -245,7 +247,7 @@ class VHttpConn(object):
         self.bans = {}
         self.freshen_pwd = 0.0
         self.hsrv = VHttpSrv(args, asrv, log)
-        self.ico = None
+        self.ico = Ico(args)
         self.ipa_nm = None
         self.lf_url = None
         self.log_func = log