Opt-in policies for OpenAI and MistralAI bots (#590)

* Define OpenAI bot ALLOW policies

Allows OpenAI bots to be allowlisted at the choice of the Anubis administrator. None are enabled by default.

* Define MistralAI bot ALLOW policy

* chore: spelling

.github/actions/spelling/expect.txt

@@ -85,6 +85,7 @@ goodbot
 googlebot
 govulncheck
 GPG
+GPT
 grw
 Hashcash
 hashrate
@@ -136,6 +137,7 @@ memes
 metrix
 mimi
 minica
+mistralai
 Mojeek
 mojeekbot
 mozilla
@@ -146,6 +148,7 @@ NONINFRINGEMENT
 nosleep
 ogtags
 onionservice
+openai
 openrc
 pag
 parseable