Upgrade OpenLayers from '6.4.3' --> '6.7.0'

[JakobMiksch]

• Upgrading to OpenLayer versions 6.5.0 and 6.6.0 worked without problem.
• The upgrade to OpenLayer 6.7.0 caused this error on npm run dev

Module parse failed: /home/jakob/Downloads/wegue/node_modules/geotiff/src/geotiff.js Unexpected token (289:35)
You may need an appropriate loader to handle this file type.
|     }
|
|     return usedImage.readRasters({ ...options, window: wnd });
|   }
| }

 @ ./~/ol/source/GeoTIFF.js 36:0-81
 @ ./~/ol/source.js
 @ ./~/babel-loader/lib!./~/vue-loader/lib/selector.js?type=script&index=0!./src/components/ol/Map.vue
 @ ./src/components/ol/Map.vue
 @ ./~/babel-loader/lib!./~/vue-loader/lib/selector.js?type=script&index=0!./app/WguAppTemplate.vue
 @ ./app/WguAppTemplate.vue
 @ ./~/babel-loader/lib!./~/vue-loader/lib/selector.js?type=script&index=0!./app/WguApp.vue
 @ ./app/WguApp.vue
 @ ./src/main.js
 @ multi ./build/dev-client ./src/main.js

> Listening at http://localhost:8081

• it could be solved with the help of this post
• upgrading to the (currently latest) OpenLayers version 6.8.0 caused this error and is not fixed yet:

this dependency was not found:                             

* txml/txml in ./~/geotiff/src/geotiffimage.js             

To install it, you can run: npm install --save txml/txml   
> Listening at http://localhost:8081