Add SCAP 1.3 source datastream schema
Add SCAP 1.3 source datastream schema

Downloaded from
https://csrc.nist.gov/schema/scap/1.3/scap-source-data-stream_1.3.xsd
Converted the EOLs to Unix using `dos2unix` tool.

OpenSCAP/openscap,OpenSCAP/openscap,OpenSCAP/openscap,OpenSCAP/openscap,redhatrises/openscap,redhatrises/openscap,redhatrises/openscap,OpenSCAP/openscap,redhatrises/openscap,OpenSCAP/openscap,redhatrises/openscap,redhatrises/openscap