(core) Add telemetry

Test Plan: Server tests.

Reviewers: jarek

Differential Revision: https://phab.getgrist.com/D3818

app/common/Telemetry.ts

@@ -0,0 +1,21 @@
+export const TelemetryTemplateSignupCookieName = 'gr_template_signup_trk';
+
+export const TelemetryEventNames = [
+  'apiUsage',
+  'beaconOpen',
+  'beaconArticleViewed',
+  'beaconEmailSent',
+  'beaconSearch',
+  'documentForked',
+  'documentOpened',
+  'documentUsage',
+  'sendingWebhooks',
+  'signupVerified',
+  'siteMembership',
+  'siteUsage',
+  'tutorialProgressChanged',
+  'tutorialRestarted',
+  'watchedVideoTour',
+] as const;
+
+export type TelemetryEventName = typeof TelemetryEventNames[number];