`rune.clone()`

[harrysolovay]

@tjjfvi's suggestion:

class Rune<T, U, A extends unknown[] = unknown[]> {
  constructor(readonly _prime: (batch: Batch) => Run<T, U>, readonly ..._arguments: A) {}

  // ...

+ clone(){
+   return new this.constructor(this._prime, ...this._arguments)
+ }
}