Support JSON serialization and deserialization of atomic.Time

[BRUHItsABunny]

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[BRUHItsABunny]

Fixes #124

[prashantv]

I think we should implement MarshalText instead, since the JSON encoding of a time is a string, and MarshalText will work in more cases, and matches atomic.String better.

[BRUHItsABunny]

Agreed, that does make more sense.
Will make the change shortly.