(core) Update design of empty docs home page, and add a "Manage Team" button.

Summary:
- Remove the empty-folder icon
- Add an "Invite team members" button for owners on empty team sites
- Add a "Browse Templates" button for all other cases on empty sites
- Update intro text for team, including a link to Sprouts
- Update intro text for personal/anon.
- Include a Free/Pro tag for team sites (for now, only "Free")
- Add a "Manage Team" button for owners on home page of all team sites.
- Polished the UI of UserManager: add a transition for the background, and
  delay the appearance of the spinner for fast loads.

Test Plan: Fixed up the HomeIntro tests; added test case for Manage Team button

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D3459

app/common/UserAPI.ts

@@ -84,6 +84,14 @@ export function getOrgName(org: Organization): string {
   return org.owner ? `@` + org.owner.name : org.name;
 }
 
+/**
+ * Returns whether the given org is the templates org, which contains the public templates.
+ */
+export function isTemplatesOrg(org: Organization): boolean {
+  // TODO: It would be nice to have a more robust way to detect the templates org.
+  return org.domain === 'templates' || org.domain === 'templates-s';
+}
+
 export type WorkspaceProperties = CommonProperties;
 export const workspacePropertyKeys = ['createdAt', 'name', 'updatedAt'];
 

app/common/gristUrls.ts

@@ -60,6 +60,7 @@ export const commonUrls = {
   help: "https://support.getgrist.com",
   plans: "https://www.getgrist.com/pricing",
   createTeamSite: "https://www.getgrist.com/create-team-site",
+  sproutsProgram: "https://www.getgrist.com/sprouts-program",
 
   efcrConnect: 'https://efc-r.com/connect',
   efcrHelp: 'https://www.nioxus.info/eFCR-Help',