added eslint prettier check to travis (#5701)

- "yarn eslint" will throw the error if there are any formatting issues
- "yarn format" will format the js file based on the project's
prettier configuration.

browser/app/js/uploads/UploadModal.js

@@ -58,7 +58,11 @@ export class UploadModal extends React.Component {
 
     return (
       <div className="alert alert-info alert--upload animated fadeInUp ">
-        <button type="button" className="close close--alt" onClick={showAbortModal}></button>
+        <button
+          type="button"
+          className="close close--alt"
+          onClick={showAbortModal}
+        />
         <div>{text}</div>
         <ProgressBar now={percent} />
         <div>