BUMP: Release alpha 2 of 6.4.0 version

package.json

 {
   "name": "gitlab-ci-dashboard",
-  "version": "6.4.0-alpha.1",
+  "version": "6.4.0-alpha.2",
   "description": "Dashboard for monitoring GitLab CI builds and pipelines for TV. This project is based on gitlab-ci-monitor by globo.com",
   "author": "Emiliano Barbosa <emilianoeloi@gmail.com>",
   "contributors": [