Make application ENV agnostic and Publish to PyPI

[sandrahoang686]

Description

This was written as an internal flex project.

We want to make stac_ipyleaflet env agnostic. The code should not be tightly coupled to any type of environment/workspace, that should be deferred as an env variable. This ticket will require a comb through of the code to make sure anything coupled to an env is decoupled. Any logic coupled, we should consider pulling it out into its own module/file. This will get us ready to publish to PyPI

Acceptance Criteria

• Make python-dotenv a dev dependency instead of an overall dependency because we only need the .env file during development
• Comb through the code to make sure anything tightly coupled to an env/workspace is pulled into its own module/file
• Any variables that need to be made as an env var should only be needed at build time, during run time, these vars can be defined in the constants file
• Think about default layers... possibly make MAAP default layers a var in constants file but do we want env agnostic users to be able to specify default layers? (If so, how can they create and specify a file?)
• Publish to PyPI (follow up - once published to PyPI, should we have MAAP and VEDA reference from there?)
• Document process of publishing to PyPI