chore: bump extension version to 1.15.2

Author: smeijer

devtools/src/manifest.json

@@ -2,8 +2,8 @@
   "manifest_version": 2,
   "name": "Testing Playground",
   "description": "Simple and complete DOM testing playground that encourage good testing practices.",
-  "version": "1.8.0",
-  "version_name": "1.8.0",
+  "version": "1.15.2",
+  "version_name": "1.15.2",
   "minimum_chrome_version": "49",
   "icons": {
     "16": "icons/16-production.png",