(core) Add Support Grist page and nudge

Summary:
Adds a new Support Grist page (accessible only in grist-core), containing
options to opt in to telemetry and sponsor Grist Labs on GitHub.

A nudge is also shown in the doc menu, which can be collapsed or permanently
dismissed.

Test Plan: Browser and server tests.

Reviewers: paulfitz, dsagal

Reviewed By: paulfitz

Subscribers: jarek, dsagal

Differential Revision: https://phab.getgrist.com/D3926

app/server/mergedServerMain.ts

@@ -119,7 +119,7 @@ export async function main(port: number, serverTypes: ServerType[],
     server.addHomeApi();
     server.addBillingApi();
     server.addNotifier();
-    server.addTelemetry();
+    await server.addTelemetry();
     await server.addHousekeeper();
     await server.addLoginRoutes();
     server.addAccountPage();
@@ -127,11 +127,12 @@ export async function main(port: number, serverTypes: ServerType[],
     server.addWelcomePaths();
     server.addLogEndpoint();
     server.addGoogleAuthEndpoint();
+    server.addInstallEndpoints();
   }
 
   if (includeDocs) {
     server.addJsonSupport();
-    server.addTelemetry();
+    await server.addTelemetry();
     await server.addDoc();
   }