[internal] Lint typescript, json, new eslint rules (#4449)

* temp 07/01/19 [skip ci] main lint files

* use lint-staged scripts

* fix all auto-fixable eslint errors

* manually fix lint issues in files

* temp 07/01/19 [skip ci]

* bump eslint plugin versions, update circle.yml

* [lint fix] remaining js files

* update vscode/settings.json

* add back stop-only

* use stop-only for linting .onlys

* fix verify_spec, build_spec

* update json plugin

* relint & apply corrections

* fix appveyor.yml not cleansing env vars (very bad)

* dont echo commit message in appveyor script

* retry build &

* re-add & upgrade lint-staged

* update contributing docs

* only let stop-only catch staged changes

packages/https-proxy/test/.eslintrc

@@ -0,0 +1,5 @@
+{
+  "extends": [
+    "plugin:@cypress/dev/tests"
+  ]
+}