Complete rewrite of idb-chunk-store

[feross]

We completely rewrote idb-chunk-store for Wormhole and it's working very well in production. It reduces the number of buffer copies and has better performance. It's also handling many edge cases better. We plan to open source it so others can use it too.

We could pick a new package name, but it might be better to just reuse idb-chunk-store since we've already been pushing our improvements into this repo. Our changes should be backwards compatible, but we can publish it as 1.0.0 just to be safe.

While we're at it, I'd like to recreate this repo so it's not listed as a fork (which hurts the repo in GitHub search and is kind of confusing since this repo has nothing to do with memory-chunk-store).

[santiagogil]

HI. Sounds great!
Do you need me to do anything about?