Add type class for lazy and strict text types

```haskell
class LazyStrict l s | l -> s, s -> l where
  toLazy :: s -> l
  toStrict :: l -> s

fromLazy :: LazyStrict l s => l -> s
fromLazy = toStrict

fromStrict :: LazyStrict l s => s -> l
fromStrict = toLazy

instance LazyStrict L.ByteString S.ByteString
instance LazyStrict L.Text S.Text
```