document Python bzip2 and lzma requirements

Linux users will need to ensure that the Python interpreter used with ComfyUI has the _bz2 standard library module enabled.

For example, Debian family users will want to install the libbz2-dev and liblzma-dev OS distribution packages. Then they may need to (re)install Python, such as with ASDF.

RHEL family users will want to perform similar steps with the libbzip2-devel and xz-devel OS distribution packages.

Otherwise, the Linux user will experience low level Python errors about missing standard library packages (_bz2 and _lzma).

A long lived Linux machine may happen to inherit these subtle dependencies from past software projects, but freshly provisioned machines may lack them, e.g. new Pop!_OS 22.04 users.