Add docs

RiotSwiftUI/Modules/Room/PollHistory/Service/PollHistoryServiceProtocol.swift

@@ -17,8 +17,14 @@
 import Combine
 
 protocol PollHistoryServiceProtocol {
-    var updates: AnyPublisher<TimelinePollDetails, Never> { get }
-    var updatesErrors: AnyPublisher<Error, Never> { get }
-    
+    /// Returns a Publisher publishing the polls in the next batch.
+    /// Implementations should return the same publisher if `next()` is called again before the previous publisher completes.
     func next() -> AnyPublisher<TimelinePollDetails, Error>
+    
+    /// Publishes updates for the polls previously pusblished by the `next()` publishers.
+    var updates: AnyPublisher<TimelinePollDetails, Never> { get }
+    
+    /// Publishes errors regarding poll aggregations.
+    /// Note: `next()` will continue to publish new polls even if some poll isn't being aggregated correctly.
+    var pollErrors: AnyPublisher<Error, Never> { get }
 }