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/string.js

@@ -9,13 +9,15 @@
  * @returns {string} Formatted string
  */
 export function padNumber(number, width, opt_precision) {
-  const numberString = opt_precision !== undefined ? number.toFixed(opt_precision) : '' + number;
+  const numberString =
+    opt_precision !== undefined ? number.toFixed(opt_precision) : '' + number;
   let decimal = numberString.indexOf('.');
   decimal = decimal === -1 ? numberString.length : decimal;
-  return decimal > width ? numberString : new Array(1 + width - decimal).join('0') + numberString;
+  return decimal > width
+    ? numberString
+    : new Array(1 + width - decimal).join('0') + numberString;
 }
 
-
 /**
  * Adapted from https://github.com/omichelsen/compare-versions/blob/master/index.js
  * @param {string|number} v1 First version