Core Rule Set: Nextcloud's ordinary requests pass by default (closes #240)

Adds nextcloud.conf, the twelfth change. Nextcloud's WebDAV paths allow
PROPFIND, PROPPATCH, MKCOL, COPY, MOVE, REPORT and SEARCH. The account-name
cookie nc_username, and the fields that carry a search, a name, a file name or
a folder on the sign-in page, the Files app, public shares and the OCS API,
skip the four rules that read them as commands or system files. Comments and
the text editor's document skip the two rules for a command after a ";" too;
932235 keeps "; wget" refused. Requests recorded from Nextcloud 35.0.2, its
web pages, sync client 3.16.7 with chunked uploads and the OCS API, pass at
the defaults and while bodies are read.

Model: opus-5-5

internal/coreruleset/coreruleset_test.go

@@ -202,7 +202,7 @@ func atDefaults(t *testing.T) *coreruleset.CoreRuleSet {
 }
 
 // wantChange checks that crs lets through passes, a request one of the
-// eleven changes is for, and still finds result in refused, a request like
+// twelve changes is for, and still finds result in refused, a request like
 // it that the change is not for.
 func wantChange(
 	t *testing.T, crs *coreruleset.CoreRuleSet, passes, refused request,