WASM compatible wallet

[thibault-martinez]

• Fix unresolved import tokio::sync::RwLock` (Add tokio features that are wasm compatible #1539)
• Fix future cannot be sent between threads safely
• Write wasm bindings

[kwek20]

Q: What wasm target are we going for?

• wasm32-unknown-unknown
• wasm32-unknown-emscripten
• wasm32-wasi

rocksdb:
Missing headers for compiling to wasm, specifically threads

• Status of rust+C bindings for wasm targets rustwasm/team#291 (comment)

Work on threads here: https://github.com/WebAssembly/threads

Stronghold:

• Missing Frag impl for wasm here:
  https://github.com/iotaledger/stronghold.rs/blob/dev/engine/runtime/src/memories/frag.rs
  https://docs.rs/wasmtime/latest/wasmtime/struct.Memory.html

Wallet.rs:

• tokio::spawn(async move ) wont work because !Send object in JsValue. Needs blocking API or mpsc(?)
  https://rustwasm.github.io/wasm-bindgen/api/src/wasm_bindgen/lib.rs.html#91
  -> Were going to use spawn_local

Ledger:

• Hidapi doesnt support wasm yet

Bindings:

• listen method