RPC support

[valzargaming]

This pull request introduces cross-platform support for connecting to Discord's IPC (Inter-Process Communication) using ReactPHP, with special handling for Windows named pipes. It adds a new example demonstrating asynchronous IPC usage, and introduces a flexible connector factory and a Windows-specific connector placeholder that guides users on enabling Windows support.

New Example and Platform Connector Abstraction:

• Added a new asynchronous example script (examples/rpc_ipc.php) that demonstrates connecting to Discord IPC using ReactPHP, handling events, and managing responses with timeouts.
• Introduced ConnectorFactory to abstract platform-specific connector creation, returning a React\Socket\Connector on Unix-like systems and a WindowsPipeConnector or null on Windows depending on support.

Windows Named-Pipe Support and Guidance:

• Added WindowsPipeConnector, a placeholder connector that provides actionable error messages if async named-pipe support is not yet available. It supports connecting via a TCP proxy (DISCORD_IPC_TCP_PROXY) or spawning a helper process (DISCORD_IPC_PROXY) to bridge named pipes, and otherwise clearly instructs users how to enable support.

[valzargaming]

This is an early-stage proof of concept and shouldn’t be merged.

I can't meaningfully test this in its current state as I do not have readily available access to my only bot that uses oauth2. I'm leaving this PR here as a draft to invite a discussion on what such an implementation could or should look like, with the expectation that a future implementation should be developed in a separate repository.