Report when thresholds are crossed during past 24 hours

Update flowalert process_data to format list of crossed thresholds

• all fires with stations that have crossed a threshold in the past 24 hours

• add method to src/flowalert/cli/process_data.py to format_threshold_summary

• update process_data function in src/flowalert/cli/flowalert.py to call new function

Example format for one station:

Threshold crossed for Monarch (mnc2020) in NV with station PNCN2.
    15 Minute Intensity: 117.856 mm/hr at 2022-06-30 12:57:00
    30 Minute Intensity: 59.436 mm/hr at 2022-06-30 13:00:00
    60 Minute Intensity: not crossed