Bump handlebars from 4.1.2 to 4.7.7 in /example/AppLinkDemo

Bumps [handlebars](https://github.com/wycats/handlebars.js) from 4.1.2 to 4.7.7.
- [Release notes](https://github.com/wycats/handlebars.js/releases)
- [Changelog](https://github.com/handlebars-lang/handlebars.js/blob/master/release-notes.md)
- [Commits](handlebars-lang/handlebars.js@v4.1.2...v4.7.7)

Signed-off-by: dependabot[bot] <support@github.com>