Documenting rc_invites.per_issuer, resolves #13330.

Signed-off-by: David Teller <[email protected]>

Author: Yoric

changelog.d/13333.doc

@@ -0,0 +1 @@
+Documenting the new `rc_invites.per_issuer` throttling option.

docs/usage/configuration/config_documentation.md

@@ -1528,6 +1528,8 @@ The `rc_invites.per_user` limit applies to the *receiver* of the invite, rather
 sender, meaning that a `rc_invite.per_user.burst_count` of 5 mandates that a single user
 cannot *receive* more than a burst of 5 invites at a time.
 
+By opposition, the `rc_invites.per_issuer` limit applies to the *issuer* of the invite, meaning that a `rc_invite.per_issuer.burst_count` of 5 mandates that single user cannot *send* more than a burst of 5 invites at a time.
+
 Example configuration:
 ```yaml
 rc_invites:
@@ -1537,6 +1539,9 @@ rc_invites:
   per_user:
     per_second: 0.004
     burst_count: 3
+  per_issuer:
+    per_second: 0.5
+    burst_count: 5
 ```
 ---
 ### `rc_third_party_invite`