large powers "underflow" to incorrect answers

You seem to be hitting some negative exponent limit and silently giving the wrong answer:
```jl
julia> (dec"0.1") .^ (10 .^ (1:10))
10-element Vector{Decimal}:
 1E-10
 1E-100
 1E-1000
 1E-10000
 1E-100000
 1E-1000000
 0E-1000026
 0E-1000026
 0E-1000026
 0E-1000026
```
Suggestion: underflow to `0.0`.