Post-processing in the High Definition Render Pipeline
The High Definition Render Pipeline (HDRP) includes its own purpose-built implementation for post-processing. This is built into HDRP, so you do not need to install any other package.
This implementation uses the Volume system. You add post-processing effects to your Camera in the same way you add any other Volume Override. Note that HDRP already enables some post-processing effects in the HDRP Global Settings, go to Section Volume Profiles.
The images below show a Scene with and without HDRP post-processing.