Function REGISTER

REGISTER(name: string, func: (...x: number[]) => number): void
Registers a custom function to use with real/complex-valued parsing.
Parameters
- name: string
  The name of the function to register
- func: (...x: number[]) => number
  The function
Returns void
Example
```
// Register factorial function
Chalkboard.REGISTER("factorial", (x) => {
  let n = 1;
  for (let i = 1; i <= x; i++) n *= i;
  return n;
});

// Returns 24
const twentyfour = Chalkboard.real.parse("factorial(4)");
```
- Defined in Chalkboard.ts:328