setup eslint with docusaurs code example

Example 1: eslint ignore

/* eslint-disable */

alert('foo');

/* eslint-enable */

Example 2: eslint ignore javascript

var thing = new Thing(); // eslint-disable-line no-use-before-define
thing.sayHello();

function Thing() {

     this.sayHello = function() { console.log("hello"); };

}