Added version number to package.json

### Description

Catapult (the internal tool we use to release Firebase JavaScript libraries) now works without the `0.0.0` version placeholder in the `package.json` file. So, we can finally add the actual version numbers back into this file.

### Code sample

N/A

package.json

@@ -1,6 +1,6 @@
 {
   "name": "firebase-tools",
-  "version": "0.0.0",
+  "version": "3.3.0",
   "description": "Command-Line Interface for Firebase",
   "main": "index.js",
   "bin": {