Add "Spokesperson" proxy type to Kusama (#430)

A "Spokesperson" is a proxy type only allowed to make remarks in the
name of the proxied account. Useful for DAOs with an account in the
relay chain that need to make a statement. This will also allow the
representative to act on behalf of the DAO in websites like
subsquare/polkassembly to edit proposals for example.

Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: fellowship-merge-bot[bot] <151052383+fellowship-merge-bot[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -18,6 +18,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - All runtimes: add `LocationToAccountApi` ([polkadot-fellows/runtimes#413](https://github.com/polkadot-fellows/runtimes/pull/413))
 - Enable Agile Coretime on Polkadot ([polkadot-fellows/runtimes#401](https://github.com/polkadot-fellows/runtimes/pull/401))
 - Add the Polkadot Coretime Chain runtime ([polkadot-fellows/runtimes#410](https://github.com/polkadot-fellows/runtimes/pull/410))
+- Kusama: Add a "Spokesperson" proxy type only allowed to send remarks ([polkadot-fellows/runtimes#430](https://github.com/polkadot-fellows/runtimes/pull/430))
 - Add the Polkadot and Kusama Coretime Chain specs ([polkadot-fellows/runtimes#432](https://github.com/polkadot-fellows/runtimes/pull/432))
 
 #### From [#322](https://github.com/polkadot-fellows/runtimes/pull/322):

relay/kusama/src/lib.rs

@@ -1037,6 +1037,8 @@ pub enum ProxyType {
 	Society,
 	#[codec(index = 8)]
 	NominationPools,
+	#[codec(index = 9)]
+	Spokesperson,
 }
 
 impl Default for ProxyType {
@@ -1135,6 +1137,11 @@ impl InstanceFilter<RuntimeCall> for ProxyType {
 					RuntimeCall::Slots(..)
 			),
 			ProxyType::Society => matches!(c, RuntimeCall::Society(..)),
+			ProxyType::Spokesperson => matches!(
+				c,
+				RuntimeCall::System(frame_system::Call::remark { .. }) |
+					RuntimeCall::System(frame_system::Call::remark_with_event { .. })
+			),
 		}
 	}
 	fn is_superset(&self, o: &Self) -> bool {