Create a cachix cache

[deemp]

Currently, for ghcjs builds, we use the miso-haskell binary cache provided by cachix.

In #126, I updated several tools, which led to cache misses. Therefore, I suggest to create a binary cache on cachix. We'll suggest contributors to fetch development tools from there (e.g., via cachix use rzk-lang).

The following credentials are necessary for caching:

• CACHIX_CACHE variable - the name of a binary cache, e.g., rzk-lang.
• CACHIX_AUTH_TOKEN secret - the cache token

[fizruk]

Created: https://app.cachix.org/cache/rzk-lang

Added CACHIX_CACHE repository variable and CACHIX_AUTH_TOKEN repository secret.

[fizruk]

By the way, we might want to build and cache GHC build as well? Or only GHCJS?

[deemp]

We can cache Nix store paths on cachix.