Feature Request: Add `clone()` method and immutable API for React compatibility

[MOhhh-ok]

Description

Currently, RRuleTemporal doesn't provide a way to create a modified copy of an existing rule instance. The options() method returns a reference to the internal options object, which can be mutated directly, but this approach has several issues:

1. No way to clone an instance: There's no built-in method to create a copy of a rule with modified options
2. React compatibility issues: Direct mutation doesn't trigger re-renders in React's state management
3. Breaks immutability patterns: Goes against modern JavaScript best practices

Use Case Example (React)

const [rule, setRule] = useState(
  new RRuleTemporal({
    freq: "MONTHLY",
    byMonthDay: [1],
    dtstart,
    count: 3,
  })
);

// This doesn't work - mutates the object but React won't re-render
rule.options().byMonthDay = [3];

// Current workaround - verbose and error-prone
setRule(new RRuleTemporal({
  ...rule.options(),
  byMonthDay: [3],
}));

Proposed Solutions

Option 1: Add a clone() method

const rule2 = rule1.clone({ byMonthDay: [3] });

Option 2: Add a with() method (similar to Temporal API)

const rule2 = rule1.with({ byMonthDay: [3] });

Option 3: Make options() return a deep copy

This would prevent accidental mutations but still doesn't solve the cloning issue.

Additional Context

This library is built on Temporal API which follows immutable patterns. It would be consistent to apply similar principles to RRuleTemporal as well.

[ggaabe]

See #92

[MOhhh-ok]

Thank you for implementing the with() method. I've confirmed that it works perfectly in React.

import { Temporal } from "@js-temporal/polyfill";
import { useState } from "react";
import { RRuleTemporal } from "rrule-temporal";

export default function App() {
  const [rule, setRule] = useState<RRuleTemporal>(
    new RRuleTemporal({
      freq: "MONTHLY",
      dtstart: Temporal.ZonedDateTime.from({
        year: 2026,
        month: 1,
        day: 1,
        timeZone: "Asia/Tokyo",
      }),
      byMonthDay: [1],
    }),
  );

  return (
    <div>
      <button
        onClick={() => {
          const newRule = rule.with({
            byMonthDay: [rule.options().byMonthDay![0] + 1],
          });
          // Verify that modifying the original rule doesn't affect newRule
          rule.options().byMonthDay = [1];
          setRule(newRule);
        }}
      >
        TEST
      </button>
      {rule.options().byMonthDay?.join(", ")}
    </div>
  );
}