Improve ESLint rules for JSX (#3608)

* Add react/no-string-refs ESLint rule

* Add react/jsx-boolean-value ESLint rule

* Add react/jsx-closing-bracket-location ESLint rule

* Add react/jsx-indent ESLint rule

* Add react/jsx-curly-spacing ESLint rule

* Add react/jsx-equals-spacing ESLint rule

* Add react/jsx-first-prop-new-line ESLint rule

* Add react/jsx-no-duplicate-props ESLint rule

* Add react/jsx-tag-spacing ESLint rule

app/javascript/mastodon/components/media_gallery.js

@@ -105,8 +105,8 @@ class Item extends React.PureComponent {
             src={attachment.get('url')}
             onClick={this.handleClick}
             autoPlay={autoPlay}
-            loop={true}
-            muted={true}
+            loop
+            muted
           />
 
           <span className='media-gallery__gifv__label'>GIF</span>