## Proposed Changes
In the continuing war against unportable binaries I figured we should have an option to enable building the Lighthouse binary itself with Milagro. This PR adds a `milagro` feature that can be used with `cargo install --path lighthouse --features milagro --force --locked`. The BLS library in-use will also show up under `lighthouse --version` like this:
```
Lighthouse 0.1.2-7d8acc20a(modified)
BLS Library: milagro
```
Future work: add other cool stuff like the compiler version and CPU target to `--version`.