Represents the "IsMap" entry of the uri action object.

It is an optional entry defined as part of the PDF 1.0 specification.

It contains a bool representing a PDF boolean object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 206, page 424.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 210, page 515.