Fixes #9 and closes #8. This adds a way to mark servers as read.

Servers are also marked as read when joining them.
You can now also mark DMs as read.

src/redux/reducers/unreads.ts

@@ -1,4 +1,5 @@
 import type { ChannelUnread } from "revolt-api/types/Sync";
+import { ulid } from "ulid";
 
 export interface Unreads {
     [key: string]: Partial<Omit<ChannelUnread, "_id">>;
@@ -11,6 +12,10 @@ export type UnreadsAction =
           channel: string;
           message: string;
       }
+    | {
+          type: "UNREADS_MARK_MULTIPLE_READ";
+          channels: string[];
+      }
     | {
           type: "UNREADS_SET";
           unreads: ChannelUnread[];
@@ -33,6 +38,17 @@ export function unreads(state = {} as Unreads, action: UnreadsAction): Unreads {
                     last_id: action.message,
                 },
             };
+        case "UNREADS_MARK_MULTIPLE_READ": {
+            const newState = { ...state };
+            const last_id = ulid();
+            for (const channel of action.channels) {
+                newState[channel] = {
+                    last_id,
+                };
+            }
+
+            return newState;
+        }
         case "UNREADS_SET": {
             const obj: Unreads = {};
             for (const entry of action.unreads) {