Reorganize the installation instructions for Magic-PDF to clarify the dependency on
detectron2 and provide a more straightforward installation process. The update includes
separating the dependency installation from the package installation and adding a note
about precompiled wheels for Python 3.10.

BREAKING CHANGE: The installation guide now assumes basic familiarity with detectron2
installation requirements. Users who need to compile detectron2 from source should refer
to the official detectron2 documentation.