Implement scalars using Annotated about strawberry

[jacobmoshipco]

Unfortunately this is can't be typed properly (See #3312, but I'd love to be wrong, I haven't spent too much time to check this)

There's a decorator form of strawberry.scalar that doesn't seem to appear in the strawberry.rocks documentation. You can use it to make properly typed version of a lot of custom scalars:

@strawberry.scalar(
    serialize=lambda v: base64.b64encode(v).decode("utf-8"),
    parse_value=lambda v: base64.b64decode(v),
)
class Base64(bytes):
    pass

Of course, this only helps if the type you want to serialize is valid as a base class, but it's something to make the type-checker happy until the annotated version is implemented.