Add a power numerical operator

**Is your feature request related to a problem? Please describe.**
According to the documentation on numerical operators (https://docs.microsoft.com/en-us/azure/azure-resource-manager/bicep/operators-numeric), the following operators are available:
\* (multiply)
\/ (divide)
\% (modulo)
\+ (add)
\- (subtract)
\- (minus)

It is however missing a power operator, which I need for some CIDR math.

**Describe the solution you'd like**
Add a power or exponent operator like ^ or ** so that `var num = 2 ^ 5` gives num = 32

The issue points to Azure's numerical-operator documentation; start by reviewing that reference and the existing Bicep numerical operators. Done means Bicep accepts a power or exponent form such as `2 ^ 5` and produces 32, with the supported syntax documented.

Written by the indexing model from the issue text.