Mandate ISO8601/RFC3339 formatted dates in incident reports

[BenWilson-Mozilla]

We received a recommendation from a member of the Mozilla community that we should mandate ISO 8601 format dates in incident reports. For example, some CAs will state in their incident report that they will be following a certain nomenclature, e.g. "DD/MM/YYYY HH:MM (All times are in MST)”, but then they don't follow that in their incident report.

[RufusJWB]

Since ISO8601 is a generic standard, I would recommend to mandate RFC3339 instead.

[BenWilson-Mozilla]

We should make this change first in the wiki - "A timeline is a date-and-time-stamped sequence of all relevant events. " here - https://wiki.mozilla.org/CA/Responding_To_An_Incident#Incident_Report