Retrieving trigger bit information from trigger_mask

In km3io, there is currently no function to retrieve the uint8 bits from the trigger_mask array using the definitions in km3io. Old functions from km3pipe exist, Shower MXShower Muon

These could be implemented in km3io so that one can call is_mx(f.events.trigger_mask) or something similar to get an Boolean array for which event contained the MX trigger (same for other triggers)