chore: Setup earthly satellite building (#29)

- Builds on main and tags will use the `medium` satellite that uses `x4`
rate on build minutes
  - This gives us larger cache and more memory
- Builds on PRs will use the `small` satellite that uses `x2` rate on
build minutes
- We are using the starter tier which gives us `10000` build minutes per
month and caching for our builds to make them faster

Earthfile

@@ -1,4 +1,5 @@
 VERSION 0.8
+PROJECT blue-build/cli
 
 IMPORT github.com/blue-build/earthly-lib/cargo AS cargo