transferables for encoder

[cpeddecord]

implementing a subset of widely available transferable objects (MDN Link) for RPC's basic encoder.

[github-actions]

We detected some changes in packages/*/package.json or packages/*/src, and there are no updates in the .changeset directory.
If the changes are user-facing and should cause a version bump, run yarn changeset to track your changes and include them in the next release CHANGELOG.
If you are making simple updates to repo configuration, examples, or documentation, you do not need to add a changeset.

[lemonmade]

I would not personally want this to be the default behavior, since it is a destructive operation that the host has no way to control. In my more modern RPC library, I added a dedicated library function that lets a consumer mark transferable properties: https://github.com/lemonmade/quilt/blob/main/packages/threads/source/transfer.ts#L9 (though I would use a WeakSet to keep track of these, if I were doing it again today).