pixi: Add some comments

Author: jorisv

scripts/activation.bat

@@ -7,6 +7,7 @@ set CMAKE_EXPORT_COMPILE_COMMANDS=1
 :: Activate color output with Ninja
 set CMAKE_COLOR_DIAGNOSTICS=1
 
+:: Set default build value only if not previously set
 if not defined EIGENPY_BUILD_TYPE (set EIGENPY_BUILD_TYPE=Release)
 if not defined EIGENPY_PYTHON_STUBS (set EIGENPY_PYTHON_STUBS=ON)
 if not defined EIGENPY_CHOLMOD_SUPPORT (set EIGENPY_CHOLMOD_SUPPORT=OFF)