Add a descriptor fuzzing dictionary.

src/test/fuzz/dict/descriptor

+"reject"
+"accept"
+"reject6"
+"accept6"
+"router"
+"ipv6-policy"
+"signing-key"
+"onion-key"
+"ntor-onion-key"
+"router-signature"
+"published"
+"uptime"
+"fingerprint"
+"hibernating"
+"platform"
+"proto"
+"contact"
+"read-history"
+"write-history"
+"extra-info-digest"
+"hidden-service-dir"
+"identity-ed25519"
+"master-key-ed25519"
+"router-sig-ed25519"
+"onion-key-crosscert"
+"ntor-onion-key-crosscert"
+"allow-single-hop-exits"
+"family"
+"caches-extra-info"
+"or-address"
+"opt"
+ "bandwidth"
+"@purpose"
+"tunnelled-dir-server"
+"-----BEGIN"
+"-----END"
+"-----"
+"ED25519 CERT"
+"RSA PUBLIC KEY"
+"CROSSCERT"
+"SIGNATURE"