Fix strict TypeScript checks for client

plugin/types/ws.d.ts

@@ -0,0 +1,24 @@
+declare module "ws" {
+  export type RawData = Buffer | ArrayBuffer | Buffer[] | string;
+
+  export class WebSocket {
+    static readonly OPEN: number;
+    constructor(url: string);
+    readonly readyState: number;
+    send(data: string): void;
+    close(code?: number, reason?: string): void;
+    terminate(): void;
+    on(event: "open", listener: () => void): this;
+    on(event: "message", listener: (data: RawData) => void): this;
+    on(event: "close", listener: (code: number, reason: Buffer) => void): this;
+    on(event: "error", listener: (error: Error) => void): this;
+    once(event: "open", listener: () => void): this;
+    once(event: "error", listener: (error: Error) => void): this;
+    off(event: "error", listener: (error: Error) => void): this;
+    removeAllListeners?(event?: string): this;
+  }
+
+  export class WebSocketServer {
+    constructor(options: { host?: string; port: number });
+  }
+}