feat(JavaScript): Support oneof

[theweipeng]

1. Fixed a performance bug that caused writeInt32 to slow down

Before:

// reader/index.ts
function writeVarInt32() {
    buffer.byteLength
}

After:

// reader/index.ts
const byteLength = buffer.byteLength;
function writeVarInt32() {
    byteLength
}

The byteLength property in a Buffer is slow to access. It appears that when we access byteLength, the V8 engine processes it using a hash lookup. so we store it in closure.

2. Support Oneof

Sometimes, the data we want to serialize does not have a confirmed type; instead, it could be one of several confirmed types. If we use an object to handle this situation, the size of the resulting binary will be too large, as it will contain much unused information.

usage:

      const oneOfThree = Type.oneof({
          option1: Type.string(),
          option2: Type.object("foo", {
              a: Type.int32()
          }),
          option3: Type.int32(),
      });
      const fury = new Fury({ refTracking: true });
      const { serialize, deserialize } = fury.registerSerializer(oneOfThree);
      const obj = {
          option1: "hello"
      }
      const input = serialize(obj);
      const result = deserialize(
          input
      );
      expect(result).toEqual(obj.option1)

[bytemain]

I think here has a wrong behavior, the deserialize result should has a kind property also, which indicates that the kind of the raw obj

[theweipeng]

I think here has a wrong behavior, the deserialize result should has a kind property also, which indicates that the kind of the raw obj

The protocol natively supports polymorphism, making a 'kind' field to describe the object type unnecessary.

[bytemain]

ok, It still can meet my needs.

[chaokunyang]

LGTM