(core) Converting server-side Comm.js to typescript

Summary:
- Add app/common/CommTypes.ts to define types shared by client and server.
- Include @types/ws npm package

Test Plan: Intended to have no changes in behavior

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3467

app/server/lib/extractOrg.ts

@@ -119,7 +119,7 @@ export class Hosts {
     }
   }
 
-  public async addOrgInfo(req: Request): Promise<RequestWithOrg> {
+  public async addOrgInfo<T extends IncomingMessage>(req: T): Promise<T & RequestOrgInfo> {
     return Object.assign(req, await this.getOrgInfo(req));
   }