Path to publishing Go modules from this repo

[rootulp]

Problem

We're currently maintaining two copies of this code. One in this repo and one in https://github.com/celestiaorg/celestia-app

Proposal

Ideally we only maintain one copy of this code. A path to maintaining one copy of the code is:

1. Publish Go modules from this repo. Optionally consider cutting a 1.0.0 release of this repo.
2. Modify celestia-app to delete the duplicate code and instead depend on modules published by this repo.

We should probably enumerate a list of issues that need to be resolved prior to publishing these Go modules.

[rootulp]

@cmwaters already cut https://github.com/celestiaorg/go-square/releases/tag/v1.0.0-rc0 and is working on using it in celestia-app. See celestiaorg/celestia-app#3026

so it seems like we don't need to enumerate a list of issues.