feat: update to poet-js 5.x (#633)

feat: upgrade node to poet-js 5.0.5

introduce jsonld-signatures to po.et claims
introduce SignedVerifiableClaim interface
inject a verifiableClaimSigner into all of the necessary containers

BREAKING CHANGE: the format of a po.et claim has changed to more closely match a VerifiableClaim signed with jsonld-signatures. This has altered the structure of the claim metadata.

Use poet-js 5.0.5 or later to generate proper claims to submit to poet-node.

References: #614
Resolves: #457

README.md

@@ -160,7 +160,8 @@ A 404 error is returned if the claim isn't found in this Node's database. This d
 Returns a paginated array of signed verifiable claims, all belonging to the passed issuer. Default limit per request is 10 claims. This is configurable with limit and offset paramaters where offset is the number of claims to skip and limit is the number of claims returned per request.
 
 ### `GET /works?offset=x&limit=x`
-Returns a paginated array of signed verifiable claims, which defaults to 10 per request. This is configurable with limit and offset parameters where offset is the number of claims to skip and limit is the number of claims returned per request.
+Returns a paginated array of signed verifiable claims, which defaults to 10 per request. This is configurable with limit 
+and offset parameters where offset is the number of claims to skip and limit is the number of claims returned per request.
 
 ### `POST /works`
 Publish a work.