Default styling configurations for the output isochrones

[SanttuVP]

Expected behaviour
It could help the user if the default style would look as follows. This is also something we could add to the documentation/Github-page of the plugin, if considered more appropriate:

This was achieved in QGIS by:

1. Ordering the layer by the isochrone_distance column as detailed in another feature request.
2. Setting Graduated as the visualization mode
3. Setting "No pen" to the stroke style (see also screenshot below)
4. Without a basemap, using the default Blending mode, and with a basemap using "Multiply" as the Blending mode

Current behaviour
Current behaviour sets the Opacity to 15 %. The visualized outcome is related to the above referenced other feature request.

Additional context

• Partly, in addition to a feature request, these are notes just to give context for the wider usage of this plugin.