(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/common/tsconfig.json

@@ -2,7 +2,8 @@
   "extends": "../../buildtools/tsconfig-base.json",
   "include": [
     "**/*",
-    "../../stubs/app/common/**/*"
+    "../../stubs/app/common/**/*",
+    "../../package.json"
   ],
   "references": [
     { "path": "../plugin" }