Bump handlebars from 4.5.3 to 4.7.7

Bumps [handlebars](https://github.com/wycats/handlebars.js) from 4.5.3 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@v4.5.3...v4.7.7)

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

package.json

@@ -14,7 +14,7 @@
     "gulp-rename": "^1.4.0",
     "gulp-replace": "^1.0.0",
     "gulp-uglify": "^3.0.1",
-    "handlebars": "^4.5.3",
+    "handlebars": "^4.7.7",
     "highlight.js": "^10.4.1",
     "jshint": "^2.9.7",
     "merge2": "^1.2.3",