Bump version prior to release

v4.1.1 release

Release v4.1.0

Release v4.0.0 with support for ol v7

Update to support OpenLayers v7. Fixes #487

The ol package now includes ES6 classes instead of transpiled ES5; in
order to extend the ol Control class ol-layerswitcher must also ship ES6
classes.

Bump version to v3.8.3

Include `src/ol-layerswitcher.css` in package to avoid breaking change

Bump version to v3.8.1

Bump version to v3.8.0

Bump to v3.8.0-beta.1