fix(package): update firebase to version 6.0.1

Closes #45

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
     "@vx/scale": "^0.0.182",
     "connected-react-router": "^6.4.0",
     "d3": "^5.9.2",
-    "firebase": "^5.11.1",
+    "firebase": "^6.0.1",
     "history": "^4.9.0",
     "lodash": "^4.17.11",
     "luxon": "^1.13.0",