Added failing test cases for dateFromString

[ErisDS]

refs #228

• These demonstrate the issue with dateFromString not working if there is a Z in dateString

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I have done a bit of debugging and discovered that it's failing on the regex.exec clause here:

mingo/src/operators/expression/date/dateFromString.ts

Line 95 in 667fc61

!new RegExp("^" + expectedPattern + "$").exec(args.dateString)

But I'm not entirely sure what that clause is meant to do so I'm a little unsure what a fix would look like.

[kofrasa]

Resolved in 6.0.5. Thanks for this test case.