Define list of env config options for subclasses.
Define list of env config options for subclasses.

Flask-Assets now no longer needs to curate that list itself.

glorpen/webassets,wijerasa/webassets,wijerasa/webassets,john2x/webassets,heynemann/webassets,JDeuce/webassets,JDeuce/webassets,0x1997/webassets,heynemann/webassets,glorpen/webassets,john2x/webassets,glorpen/webassets,scorphus/webassets,aconrad/webassets,heynemann/webassets,0x1997/webassets,scorphus/webassets,florianjacob/webassets,aconrad/webassets,florianjacob/webassets,aconrad/webassets