Support aeson 2.0

[bitc]

aeson 2.0 has breaking changes. Here is the error I got:

src/ADL/Core/Value.hs:181:77: error:
    • Couldn't match type ‘Data.Aeson.KeyMap.KeyMap JS.Value’
                     with ‘HM.HashMap T.Text JS.Value’

I found this migration guide that may help: https://github.com/haskell/aeson/issues/881#issuecomment-944920664