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/vec/mat4.js

@@ -2,7 +2,6 @@
  * @module ol/vec/mat4
  */
 
-
 /**
  * @return {Array<number>} "4x4 matrix representing a 3D identity transform."
  */
@@ -10,7 +9,6 @@ export function create() {
   return [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1];
 }
 
-
 /**
  * @param {Array<number>} mat4 Flattened 4x4 matrix receiving the result.
  * @param {import("../transform.js").Transform} transform Transformation matrix.