To prevent serialization issues, this commit narrows the type of the `presence`
object `P`. Previously, `<P extends Indexable>` allowed any value type, 
including non-JSON serializable ones like byte arrays, Date, and Long.

We now introduce a `Json` type, inspired by Liveblocks, to ensure only JSON
serializable types are allowed in the presence object. This change affects
functions like `broadcast`, ensuring safe serialization and addressing 
issues such as #884.

The new `Json` type is defined as follows:

```
export type Json = JsonPrimitive | JsonArray | JsonObject;
type JsonPrimitive = string | number | boolean | null;
type JsonArray = Array<Json>;
type JsonObject = { [key: string]: Json | undefined };
```

This type restriction enhances type safety and prevents potential runtime 
errors during JSON serialization of presence data.

---------

Co-authored-by: Youngteac Hong <susukang98@gmail.com>

Implement a new BroadcastOptions interface to allow for automatic retries
on network failures during broadcasts. This enhancement improves resilience
against temporary network issues, ensuring more reliable message delivery.
The maxRetries option allows users to control retry behavior, with a default
of 0 (no retries). Only network errors trigger retries; other errors, such
as unserializable payloads, will not initiate retry attempts.

Enhance splay tree efficiency by incorporating splay operations after node
location in Find and IndexOf functions. This change maintains the tree's
self-balancing property and ensures amortized O(log n) time complexity for
future operations. Simplify IndexOf() by leveraging the splay operation,
reducing additional traversal logic and improving overall performance.

This commit Streamlines data type handling by replacing Long with native.
It also updates target to ECMAScript 2020.

Despite the introduction of bigint, but Long still remains in Counter. We
need to remove Long.