`napi_get_buffer_info` always supported receiving `Uint8Array` as a
`value` argument because `node::Buffer` is a subclass of `Uint8Array`
and the underlying V8 APIs don't distinguish between two. With this
change we mark both types as supported by the API so that the user code
doesn't have to unknowingly use oficially unsupported type of the
`value` argument.

Co-authored-by: Chengzhong Wu <legendecas@gmail.com>