Core Rule Set: Mastodon's ordinary requests pass by default (closes #238)

Adds mastodon.conf, the twelfth change. On Mastodon's paths, the fields
that carry a search, a name, a title, an address, a password or free text
skip the four rules that read them as commands or system files. They cover
the API and the web app's JSON, the admin and settings pages, sign-up and
sign-in, and the objects other servers deliver to an inbox. A post's text
skips 932125, 932230 and 932235 too. Hashtags and sign-up usernames skip
only 932120 and 932260. Uploaded file names skip 932180, a report's
forward keys skip 930120 by name, and the Accept header of a link lookup
skips 920600 on profile and post links. The requests recorded from
Mastodon 4.7.5 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,