Add temporary tag until v2.0.0 is officially released

Make sure to remove this before publishing v2.0.0 stable,
or dist-tags will have to be updated manually on npm
afterwards.

package.json

@@ -2,6 +2,9 @@
   "name": "thelounge",
   "description": "The self-hosted Web IRC client",
   "version": "2.0.0-pre.1",
+  "publishConfig": {
+    "tag": "next"
+  },
   "preferGlobal": true,
   "bin": {
     "lounge": "index.js"