Add popover detection script and no-popover html class

Author: JoelCDL

src/js/main.js

@@ -2,6 +2,7 @@ import './anchor-positioning.js'
 import './headernav.js'
 import './mediaqueries.js'
 import './newsreel.js'
+import './popover-support.js'
 import './sidebarposts.js'
 import './slideshow.js'
 import './toggles.js'

src/js/popover-support.js

@@ -0,0 +1,7 @@
+// ***** Popover Support for CSS ***** //
+
+// If the popover element is detected in the browser, remove the no-popover class from the html tag.
+
+if (window.HTMLElement.prototype.hasOwnProperty('popover')) { // eslint-disable-line no-prototype-builtins
+  document.querySelector('html').classList.remove('no-popover')
+}