Add an example for Encoding and Decoding abilities

[lukewilliamboswell]

No description provided.

[faldor20]

Hey, I am slightly concerned that this shows a very inefficient way of decoding and encoding this type. I appreciate you may want to show how the internals work, but it's not really showing best practices. perhaps if we want to show complex encoding and decoding we should pick a type that should be decoded that way

eg: For the encoder it should probably look like this:

encodeItems : ItemKind -> Encoder fmt
encodeItems = \@ItemKind tag ->
    when tag is
        Text -> 1
        Method -> 2
        Function -> 3
        Constructor -> 4
        Field -> 5
        Variable -> 6
        Class -> 7
        Interface -> 8
        Module -> 9
    |>Encode.u8

[bhansconnect]

I think it is totally fine to merge as is, but some listed nit comments would be nice to address.

[lukewilliamboswell]

Updated with @faldor20 changes, thanks ❤️ 🇦🇺 🦘 . I think this is a much improved example.