Proposal - Code splitting / modularization

Is your feature request related to a problem? Please describe.

No issue in particular, other than not easily being able to easily omit certain pieces of functionality.
We offer a 'light' build that currently removes:

• alt-audio support
• subtitles support
• EME support

However depending on the combination of features desired (e.g. if someone wants EME support but not subtitles or alt-audio support) they're either forced to build from source with local code modifications or use the main fully-featured build.

Describe the solution you'd like

Perhaps a 'plugin' system - where core functionality stays in place and utilizes a set of provided plugins.

Further design details TBD

Describe alternatives you've considered

None. Are there any other alternative approaches to tackle this?

Additional context

We should still always provide the main and light builds for the folks that want them.

It would be really slick if we also have the ability to easily build from source with a selectable list of features, so no local code modifications are needed.

As well, we could come up with some other pre-built options to offer alongside the main and light builds.

No files, tests, or entry points are named. Start by reviewing how the current main and light builds select features, then define the selectable build options and verify that both existing builds remain available.