(core) show package.json version when hovering on Grist icon in grist-core

Summary:
This makes the version shown when hovering on the Grist icon equal
the version set in package.json, for a grist-core build. Previously
the number shown was a hard-coded placeholder.

The Grist SaaS build has some build machinery dealing with the
version number that should be unaffected by this change for now.

Test Plan: tested manually with build_core.sh

Reviewers: jarek

Reviewed By: jarek

Differential Revision: https://phab.getgrist.com/D3659

app/server/companion.ts

@@ -1,3 +1,4 @@
+import { version } from 'app/common/version';
 import { synchronizeProducts } from 'app/gen-server/entity/Product';
 import { HomeDBManager } from 'app/gen-server/lib/HomeDBManager';
 import { applyPatch } from 'app/gen-server/lib/TypeORMPatches';
@@ -43,6 +44,7 @@ export function getProgram(): commander.Command {
   addHistoryCommand(program, {nested: true});
   addSiteCommand(program, {nested: true});
   addSqliteCommand(program);
+  addVersionCommand(program);
   return program;
 }
 
@@ -160,6 +162,12 @@ export function addSqliteCommand(program: commander.Command) {
     .action(filename => new Gristifier(filename).degristify());
 }
 
+export function addVersionCommand(program: commander.Command) {
+  program.command('version')
+    .description('show Grist version')
+    .action(() => console.log(version));
+}
+
 // Report the status of the database. Migrations appied, migrations pending,
 // product information applied, product changes pending.
 export async function dbCheck(connection: Connection) {