Automatically bundle the code of pinned val versions

[pomdtr]

Currently pinned imports are broken, since only the root val version is fixed.

To solve this, I propose to bundle the code of all vals in the dependency tree each time a new version of a val is created, and serve this bundle when importing a pinned version:

import "https://esm.town/pomdtr/val" // keep the same behaviour as today
import "https://www.val.town/v/pomdtr/gfm?v=3" // import a bundle generated a long time ago. The code will always stay the same.

[easrng]

This will break vals that rely on brand checks or side effects.