Merge some things from `ashley-compile-to-wasm` (#687)

* Make availability-store compile for WASM

* Use --manifest-path instead

* Make validation work on wasm!

* Switch to Spawn trait

* Migrate validation to std futures

* Migrate network to std futures

* Final changes to validation

* Tidy up network

* Tidy up validation

* Switch branch

* Migrate service

* Get polkadot to compile via wasm!

* Add browser-demo

* Add initial browser file

* Add browser-demo

* Tidy

* Temp switch back to substrate/master

* tidy

* Fix wasm build

* Re-add release flag

* Add the /ws bootnode to the chain specs

* Copy changes from master

* Switch branch

* Switch libp2p and add wasm-timer

* Switch back libp2p and add rand

* Fix bootnodes PeerIds

* use browser indexdb

* Reduce changeset