[DRAFT] Distribute as a hex package

[sheerlox]

Description

As suggested by @D4no0 in its response to the Elixir Forum announcement, distributing semantic-release and semantic-release-hex as a bundled hex package (similarly to how Phoenix's tailwind package is working) would enable:

• eliminating the need for users to have Node.js installed
• streamlining the installation process (not needing to run npm install commands, not maintaining package.json & package-lock.json)
• configuring through the standard mix.exs project file (instead of in package.json or .releaserc, although the latter would probably be the temporary solution of choice while the mix.exs configuration feature is implemented)
• publishing Elixir-specific documentation for the package to hexdocs.pm

Feature specification (WIP)

Depends on

• semantic-release standalone executables (see Bridging between Elixir and `semantic-release` semantic-release/semantic-release#3069)

Resources

• https://github.com/phoenixframework/tailwind
• https://github.com/tailwindlabs/tailwindcss/blob/master/standalone-cli