deps: use TS multiformats

[maschad]

do not merge

Related #2152

[maschad]

@wemeetagain I am getting some module not found errors despite them appearing on the file system, I am not sure if it's related to how the types are exported

[achingbrain]

I think multiformats is not being built on install? It's a GH branch dependency here so it's coming down as raw typescript, it needs to be transpiled to js before it'll work - the multiformats module needs a prepare script or smth.

Just, we need to be careful with prepare because it runs during npm i locally so if there's some ts breakage in dom.d.ts or whatever it'll break installing deps when doing local multiformats development 😩

It also pulls down all dev deps when used as a GH dependency (vs npm dependency) so can be absurdly heavy, and mean multiple versions of aegir being installed and other such 🤮 .

[maschad]

Good call @achingbrain the tests are passing now.

@wemeetagain I've updated multiformats/js-multiformats#251