Add primer-miso artifacts to the repo

[dhess]

It would be very useful to store primer-miso artifacts in the repo:

• It would make deployments trivial, as there are numerous tools that support deploying static sites from a git repo.
• It would be trivial to spin up the exact version of the web app corresponding to a particular git ref.
• Due to the immutability of git history, it’s a more secure way to distribute artifacts than GitHub releases, not to mention that it doesn’t depend on GitHub in any way.

It might consume quite a bit of storage, but we can use git-lfs to minimize the impact.

[dhess]

I considered creating a separate “releases” repo, but that would eliminate one of the primary benefits of this approach, which is a trivial 1:1 correspondence of artifact to Primer git ref.

[dhess]

If haskell.nix gets Wasm support soon (input-output-hk/haskell.nix#2351), we probably won't need to do this, as we'll be able to store the Wasm dists in Nix, and that would accomplish the same goals.