Make code prettier

This updates ESLint and our shared eslint-config-openlayers to use Prettier.  Most formatting changes were automatically applied with this:

    npm run lint -- --fix

A few manual changes were required:

 * In `examples/offscreen-canvas.js`, the `//eslint-disable-line` comment needed to be moved to the appropriate line to disable the error about the `'worker-loader!./offscreen-canvas.worker.js'` import.
 * In `examples/webpack/exapmle-builder.js`, spaces could not be added after a couple `function`s for some reason.  While editing this, I reworked `ExampleBuilder` to be a class.
 * In `src/ol/format/WMSGetFeatureInfo.js`, the `// @ts-ignore` comment needed to be moved down one line so it applied to the `parsersNS` argument.

src/ol/events.js

@@ -3,7 +3,6 @@
  */
 import {clear} from './obj.js';
 
-
 /**
  * Key to use with {@link module:ol/Observable~Observable#unByKey}.
  * @typedef {Object} EventsKey
@@ -51,7 +50,7 @@ export function listen(target, type, listener, opt_this, opt_once) {
   }
   if (opt_once) {
     const originalListener = listener;
-    listener = function() {
+    listener = function () {
       target.removeEventListener(type, listener);
       originalListener.apply(this, arguments);
     };
@@ -59,13 +58,12 @@ export function listen(target, type, listener, opt_this, opt_once) {
   const eventsKey = {
     target: target,
     type: type,
-    listener: listener
+    listener: listener,
   };
   target.addEventListener(type, listener);
   return eventsKey;
 }
 
-
 /**
  * Registers a one-off event listener on an event target. Inspired by
  * https://google.github.io/closure-library/api/source/closure/goog/events/events.js.src.html
@@ -90,7 +88,6 @@ export function listenOnce(target, type, listener, opt_this) {
   return listen(target, type, listener, opt_this, true);
 }
 
-
 /**
  * Unregisters event listeners on an event target. Inspired by
  * https://google.github.io/closure-library/api/source/closure/goog/events/events.js.src.html