Publish stable rain-math-float to crates.io #216

`rain-math-float` is on crates.io at `0.1.1-alpha.2`. Raindex consumes via path-dep:

```toml
rain-math-float = { path = "lib/rain.interpreter/lib/rain.interpreter.interface/lib/rain.math.float/crates/float" }
```

Want a stable release so raindex (rainlanguage/raindex.deploy#2586) can pin a version instead of carrying the submodule.