configure karma to use chromium

Author: theinterned

test/karma.config.js

@@ -1,3 +1,6 @@
+// eslint-disable-next-line no-undef
+process.env.CHROME_BIN = require('chromium').path
+
 function reply(request, response, next) {
   if (request.method === 'GET') {
     if (request.url.startsWith('/500')) {