Release 6.0.0-beta2

Release 6.0.0-beta1

Release 6.0.0-beta

Merge branch '87-flatmap-for-m3system' into 'main'

Resolve "FlatMap (for M3System)"

Closes #87 and coal/m3system#8

See merge request oscar/oscar-cbls!80

Last version of OscaR.cbls as it was before migration