Can't use iroh-blobs with iroh-irpc on WASM

[m11m]

Currently the iroh-blobs/rpc feature needs to be enabled when iroh-blobs is used alongside irpc-iroh. This does not work in WASM as the feature also enables some tokio code.

Example: https://github.com/m11m/iroh-irpc-wasm-example/blob/main/Cargo.toml

[cbenhagen]

@rklaehn I am in the same boat here. We'd also like to target wasm soon and are using both iroh-blobs (through iroh-docs) and iroh-rpc. Is there anything I can do to help move this forward?