Prepare for release 2.3.1 (#294)

9 jobs for master in 18 minutes and 59 seconds (queued for 5 seconds)
Name Stage Failure
miri Test
error: aborting due to previous error

error: test failed, to rerun pass '--lib'

real 0m57.156s
user 1m23.319s
sys 0m8.453s
Cleaning up file based variables
ERROR: Job failed: exit code 1