meta: introduce Cypress end-to-end testing (via #4827)

* `test/e2e` -> `test/e2e-selenium`

* add Cypress

* ESLint fixes

* MOAR cypress

* `integration` -> `tests`

* wire Cypress up to a hot e2e server

* linter fixes

* don't run in CI

test/e2e-selenium/nightwatch.json

@@ -0,0 +1,59 @@
+{
+  "src_folders" : ["test/e2e/scenarios"],
+  "output_folder" : "reports",
+  "live_output": true,
+  "custom_commands_path" : "",
+  "custom_assertions_path" : "",
+  "page_objects_path" : "test/e2e/pages",
+  "globals_path" : "",
+
+  "test_runner" : {
+    "type" : "mocha",
+    "options" : {
+      "ui" : "bdd",
+      "reporter" : "list"
+    }
+  },
+
+  "selenium" : {
+    "start_process" : true,
+    "server_path" : "node_modules/selenium-server-standalone-jar/jar/selenium-server-standalone-3.12.0.jar",
+    "log_path" : "",
+    "host" : "127.0.0.1",
+    "port" : 4444,
+    "cli_args" : {
+      "webdriver.chrome.driver" : "node_modules/chromedriver/bin/chromedriver",
+      "webdriver.firefox.profile" : "",
+      "webdriver.ie.driver" : ""
+    }
+  },
+
+  "test_settings" : {
+    "default" : {
+      "launch_url" : "http://localhost",
+      "selenium_port"  : 4444,
+      "selenium_host"  : "localhost",
+      "silent": true,
+      "screenshots" : {
+        "enabled" : false,
+        "path" : ""
+      },
+      "desiredCapabilities": {
+        "browserName": "chrome",
+        "marionette": true
+      }
+    },
+
+    "chrome" : {
+      "desiredCapabilities": {
+        "browserName": "chrome"
+      }
+    },
+
+    "edge" : {
+      "desiredCapabilities": {
+        "browserName": "MicrosoftEdge"
+      }
+    }
+  }
+}