perf: update popper.js install method

This commit updates how the auro-popover element consumed the library
popper.js code to better support ESM/SSR development environments.

NOTE: This update does not 100% solve the issues we have with popper.js.
This version of the library is deprecated and the owners of it have
moved to a new platform, Floating UI.

This element will still require upgrading to either a new library tool
or support native popover browser support.

Changes to be committed:
modified:   src/auro-popover.js
modified:   src/popover.js

src/auro-popover.js

@@ -11,7 +11,7 @@ import { LitElement, html, css } from "lit";
 // Import touch detection lib
 import styleCss from "./style-css.js";
 
-import Popover from "./popover";
+import Popover from "./popover.js";
 
 /**
  * Popover attaches to an element and displays on hover/blur.

src/popover.js

@@ -5,7 +5,7 @@
 
 /* eslint-disable max-params */
 
-import { createPopper } from '@popperjs/core/dist/esm/popper';
+import { createPopper } from '@popperjs/core';
 
 // build the component class
 const popoverOffsetDistance = 18,