SelectCluster caclulations should consider user projection

[RamZal365]

Hi there,

We are using the animatedCluster feature of ol-ext in our project, and we realized that the animations and the final location of the points for the selectCluster interaction only work for the default projection (ESPG:3587). In our case we are using the function useGeographic (https://openlayers.vip/apidoc/module-ol_proj.html#.useGeographic) to make it so the map view uses geographic coordinates (even if the view projection is not geographic).

After debugging a bit, we realized that the error is found in the variables pix and res (lines 203 and 282 of SelectCluster.js) where it is assumed the Projection of the points to be the one of the View.

A fix suggestion would be to leverage the function getUserProjection to transform the resolution using the user's projection:
this.getMap().getView().getResolution() * this.getMap().getView().getProjection().getMetersPerUnit() / getUserProjection().getMetersPerUnit()

This is my first issue here, hope I made it clear enough, let me know if more info is required.
Thanks

[Viglino]

Last commit should solve the issue.