Extend get Method to Support Callbacks

[Daniel-Boll]

The current implementation of the get method in axum-js only accepts a string argument for specifying the path. To enhance its functionality and align with common JavaScript/TypeScript practices, it is essential to extend the get method to also accept a callback function. This callback function should be executed when the route is accessed.

Currently:

app.get('/', (req, res) => {
  res.send('Hello World!')
});

The callback function provides a mechanism to handle requests and send responses, enabling more dynamic and interactive API endpoints.

Acceptance Criteria:

• Update the get method to accept a callback function as an argument alongside the path string.
• Ensure the callback function is executed when the specified route is accessed.
• Update any relevant documentation, type definitions, and tests to reflect this change.
• Ensure the implementation adheres to the project's STYLE_GUIDE.md and is consistent with existing code patterns.
• Create a PR with the necessary code changes, updated documentation, and tests.

Additional Context:

Supporting callbacks is a step towards making axum-js more flexible and user-friendly, aligning with common patterns used in JavaScript and TypeScript-based server frameworks.