Add a `browser-utils` crate (#4394)

* Squash

* Fix keystore on wasm

* Update utils/browser/Cargo.toml

Co-Authored-By: Benjamin Kampmann <[email protected]>

* export console functions

* Use an Option<PathBuf> in keystore instead of cfg flags

* Add a KeystoreConfig

* Update libp2p

* Bump kvdb-web version

* Fix cli

* Upgrade versions

* Update wasm-bindgen stuff

Co-authored-by: Benjamin Kampmann <[email protected]>