This patch adds support to export and import grease pencil in several formats. Inlude: * Export SVG * Export PDF (always from camera view) * Import SVG The import and export only support solid colors and not gradients or textures. Requires libharu and pugixml. For importing SVG, the NanoSVG lib is used, but this does not require installation (just a .h file embedded in the project folder) Example of PDF export: https://youtu.be/BMm0KeMJsI4 Reviewed By: #grease_pencil, HooglyBoogly Maniphest Tasks: T83190, T79875, T83191, T83192 Differential Revision: https://developer.blender.org/D10482