Don't include the world in the published packages

We ended up including all sorts of stuff in our published packages. Let's take
the opposite approach and include useful stuff rather than exclude unuseful
stuff.

.npmignore

@@ -1,3 +0,0 @@
-example
-examples
-build/.module-cache

package.json

@@ -8,6 +8,19 @@
     "url": "https://github.com/vector-im/vector-web"
   },
   "license": "Apache-2.0",
+  "files": [
+    "AUTHORS.rst",
+    "CONTRIBUTING.rst",
+    "deploy",
+    "docs",
+    "karma.conf.js",
+    "lib",
+    "release.sh",
+    "scripts",
+    "src",
+    "test",
+    "webpack.config.js"
+  ],
   "style": "bundle.css",
   "matrix-react-parent": "matrix-react-sdk",
   "scripts": {
@@ -29,7 +42,7 @@
     "start": "node scripts/babelcheck.js && parallelshell \"npm run start:emojione\" \"npm run start:js\" \"npm run start:skins:css\" \"http-server -c 1 vector\"",
     "start:prod": "parallelshell \"npm run start:emojione\" \"npm run start:js:prod\" \"npm run start:skins:css\" \"http-server -c 1 vector\"",
     "clean": "rimraf build lib vector/olm.* vector/bundle.* vector/emojione",
-    "prepublish": "npm run build:css && npm run build:compile",
+    "prepublish": "npm run build:compile",
     "test": "karma start --single-run=true --autoWatch=false --browsers PhantomJS --colors=false",
     "test:multi": "karma start"
   },