[Feature Request]: apply theme to create_polar_markers prior to saving PNG figures

[mooibroekd]

The function create_polar_markers is also responsible for the creation of the PNG figures that are plotted on the map. The PNG figures are based on the openair::polarPlot function.

I would like to make the radial lines solid instead of dashed.

[mooibroekd]

https://github.com/davidcarslaw/openairmaps/issues/37#issuecomment-1494089570

This would also allow the change of the line type of the radial lines, as defined in lines 1138 - 1143 of the openair::polarPlot function by setting the lty=1.