Lock swagger-client dependency version

Fix a case of misusing findIndex.

Don't render Markdown if input or sanitized input is empty

Update and pin yaml-js version

Add back shallowEqualKeys ( editor depends on it )

Add `Good first contribution` message

Replace babel-polyfill with transform-runtime

don't use ES6 syntax in a dist package

using ES6 syntax will cause trouble unless you transpile before use (which is something you should not be required to do in a dist package)

This is needed for whatwg-fetch + IE11.
An alternative is to include "node_modules/whatwg-fetch" in the
transform-runtime.
But my guess is that someone is likely going to add a lib that in turn
uses Promises, without adding it to the whitelist. This is safter.

v/3.0.16

Fix wrong path to absolute-path.js

Path should be "./absolute-path.js" not "./.absolute-path.js". This caused webpack to throw an error "/node-modules/swagger-ui-dist/.absolute-path.js doesn't exist"

v/3.0.15

nano is questionable.

Render Markdown for object and property descriptions

#2946 Fix