Fix allow listed files for what to include in npm package

When #296 was merged, the list of files to include in `package.json` was not updated. This PR fixes that.

The `.npmignore` file is also removed because I find it causes some unexpected behaviors like ignoring the contents of `.gitignore`. It's a bit of extra work to maintain the allow listed `files` but it's generally safer.

package.json

@@ -79,10 +79,9 @@
   "main": "./dist/cookie/index.js",
   "types": "./dist/cookie/index.d.ts",
   "files": [
-    "dist/*.js",
-    "dist/*.d.ts",
-    "dist/cookie/*.js",
-    "dist/cookie/*.d.ts"
+    "dist/**/*.js",
+    "dist/**/*.d.ts",
+    "!__tests__"
   ],
   "scripts": {
     "build": "npm run clean && tsc",