Consider adding a dynamic effect

[tbidne]

Hello, thanks for the nice library.

Recently I had cause to use a dynamic variant of the typed-process effect. In particular, I had a test suite that relied on mocking, so I ended up with something like:

runTypedProcessMock :: Eff (TypedProcess : es) a -> Eff es a
runTypedProcessMock = interpret_ $ \case
  -- processConfigToCmd :: ProcessConfig i o e -> String
  ReadProcess pc -> case processConfigToCmd pc of
     "expected_cmd" -> pure (ExitSuccess, "expected output", "")
  ...

This, of course, relies on having a dynamic TypedProcess, as opposed to the static one. Do you have any interest in me upstreaming this here? The code is a straightforward translation of the static module, so I don't think it will add much of a maintenance burden. If so, I'll open a PR. If not, no worries, I'll continue to use my local implementation.