Build read only nodes for each build

[nitro-neal]

Additionally we need read only nodes:

Build read only nodes for each build

Config to turn roles on and off:
https://github.com/decentralized-identity/ion/blob/master/config/mainnet-core-config.json

Change both batchingIntervalInSeconds (for Batch Writer) and observingIntervalInSeconds (for Observer) to 0, then you have an ION node running just the Resolver.

Unit test:
https://github.com/decentralized-identity/sidetree-reference-impl/blob/bf1f7aeab251083cfb5ea5d612f481cd41f0ab1b/tests/core/Core.spec.ts#L108

[nitro-neal]

#11