Dockerized

[manicprone]

This PR includes:

• Dockerization of the API server (with useful npm scripts for local dev).
• A GitHub action for build/publish of the Docker image (currently not using a version cycle).
• A systemDefaults.js to manage default values that are supported.
• A /status GET endpoint for a simple health check (which requests the electrs /blocks/tip/height endpoint)
• A pre-commit hook to ensure linting passes before commit.

The main point of this PR is to make my work visible (not necessarily to merge into the trunk branch). But, it can be merged in safely. I am currently using this with the AWS setup.

Future items:

• Update the CI/CD pipeline to build/push on version updates of the code. Currently performs this action whenever pushed to a branch named: dockerized.
• Update README to include relevant info on docker usage.