Add pdsg (palladium spirv-generator)

- remove glslang from pd-system
- use spirv blobs instead of glsl 460
- Use Legacy shaders for OpenGL2 backend
- add devnotes

tools/CMakeLists.txt

@@ -3,4 +3,5 @@ cmake_minimum_required(VERSION 3.22)
 add_subdirectory(lazyvec)
 add_subdirectory(ppam)
 add_subdirectory(pdlm)
-add_subdirectory(pdfm)
+add_subdirectory(pdfm)
+add_subdirectory(pdsg)