Feature request: PSS (proportional set size) and PSSWP (proportional swap share)

[shvchk]

Similar to htop:

[M_PSS (PSS)](https://manpages.debian.org/testing/htop/htop.1.en.html#M_PSS)
    The proportional set size, same as M_RESIDENT but each page is divided by the number of processes sharing it.
[M_M_PSSWP (PSSWP)](https://manpages.debian.org/testing/htop/htop.1.en.html#M_M_PSSWP)
    The proportional swap share of this mapping, unlike M_SWAP this does not take into account swapped out page of underlying shmem objects.

• https://manpages.debian.org/testing/htop/htop.1.en.html#M_PSS
• https://github.com/htop-dev/htop