Implement EsploraExt for esplora_client::AsyncClient

[danielabrozzoni]

Describe the enhancement

bdk/crates/esplora/src/lib.rs

Lines 309 to 318 in 9763132

	fn scan<K: Ord + Clone>(
	&self,
	_local_chain: &BTreeMap<u32, BlockHash>,
	_keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, Script)>>,
	_txids: impl IntoIterator<Item = Txid>,
	_outpoints: impl IntoIterator<Item = OutPoint>,
	_stop_gap: usize,
	_parallel_requests: usize,
	) -> Result<KeychainScan<K, ConfirmationTime>, Error> {
	todo!()

Use case
Using bdk_esplora in wasm

[evanlinjin]

This is done in #885 which is merged into #793. Essentially, we now have EsploraAsyncExt.