log-viewer-webui: Serve client using server in production; Add npm scripts to setup, lint, and start client and server together during development.

[kirkrodrigues]

Description

This PR:

• Adds code to serve the client (from CLIENT_DIR) using the server, but only in production mode.
  • For ease of development, in development mode, the client will be served using a webserver that supports hot module replacement.
  • When the client is updated to call server APIs, we will pass in an env var which indicates the server's address.
• Adds npm scripts to init, lint, and run the client and server together.
• Updates the docs about the points above.
• Applies the linter to fix some violations from #468.

Validation performed

Validated all the new npm scripts work.