Add the Javascript double asterisk power operator (**) to the list of supported features

[DonaldDuck313]

The double asterisk operator (**) is Javascript is a recent operator for powers (for example 2**3 becomes 8). It would be nice to know which browsers support it.

[Schweinepriester]

• https://caniuse.com/#feat=mdn-javascript_operators_arithmetic_exponentiation
• https://kangax.github.io/compat-table/es2016plus/#test-exponentiation_(**)_operator
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Exponentiation

TL;DR: Works ~everywhere except IE.