Represents the "Lang" entry of the annotation dictionary object.

It is an optional entry defined as part of the PDF 2.0 specification.

It contains a string representing a PDF string object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 164, page 383.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 166, page 467.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 252, page 467.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 255, page 565.

The language tag specifies the natural language of the annotation's text content in BCP 47 format, overriding any language specified at the page or document level.