Add flyweight type for the native browser Blob type.
Add flyweight type for the native browser Blob type.

This fixes things like foam.util.clone() for native browser File and Blob types rather than having to apply cloneProperty to every property that may want to hold these types.

foam-framework/foam2,foam-framework/foam2,foam-framework/foam2,foam-framework/foam2,foam-framework/foam2,jacksonic/vjlofvhjfgm,jacksonic/vjlofvhjfgm,jacksonic/vjlofvhjfgm