Support multiple libraries

[cgeorgii]

Description

According to the manual:

Packages may contain multiple components: an optional library and any number of executables, test suites or benchmarks (Cabal does support multiple libraries now, but Hix doesn’t yet).

The wording makes me believe that this is desirable to you as it would be to me, so I decided to open this ticket to track this effort and maybe help out.

hpack seems to support it via the internal-libraries field, as seen here.

Extra context

• Announcement post for supporting multiple components in cabal
• Add support for loading multiple components into one repl session haskell/cabal#8726
• hpack: Quick-reference - Top-level fields

[tek]

implemented!