[Website] Distinguish emeritus members in governance page

[asfimport]

Currently, emeritus members are not marked as such in the governance page.
(see comment by [~tlipcon] at apache/arrow-site#172 (review))

We should probably improve our check_committers.py script to look for emeritus members using the ASF's Web services.

Reporter: Antoine Pitrou / @pitrou

_{Note: This issue was originally created as ARROW-15094. Please see the migration documentation for further details.}

[thisisnic]

This issue has been closed due to having no activity since 2021 or earlier. Feel free to reopen if this has been closed in error.