- Migrated Sleeper implementation from `gloo-timers` to async runtime-agnostic `futures-timer`

- Adjusted feature flags and updated dependencies to reflect this change, ensuring seamless functionality across different environments:

  - `gloo-timers-sleep` feature kept for backwards compatibility, it will imply the automatically `futures-timer-sleep`

  - if `wasm32` architecture is detected, it automatically enables the `gloo-timers` feature on `futures-timer` crate to ensure WASM compatibility.

Closes Xuanwo#153

…feature/add-futures-timer