fix: cabal warning

[Unisay]

Fix by using a common stanza with ghc options and a default language:

Warning: [no-default-language] Packages using 'cabal-version: >= 1.10' and
before 'cabal-version: 3.4' must specify the 'default-language' field for each
component (e.g. Haskell98 or Haskell2010). If a component uses different
languages in different modules then list the other ones in the
'other-languages' field.