Bump package version

Bump copyright year

Bump package version

Release 0.8.9.4 with multipart/form-data

Bump resolver to lts-18.0

Bump resolver to lts-16.6

Long overdue

Expose internal modules

Internal modules are exposed so the test suite now only depends on the
library and not the code in lib/ directly. Internal modules are _not_
visible in the generated Haddock documentation.

Clear stack sdist warnings

Clear package check warnings