Log Message:
lang/janet: Update to 1.30.0

## 1.30.0 - 2023-08-05

- Change indexing of `array/remove` to start from -1 at the end instead of -2.
- Add new string escape sequences `\\a`, `\\b`, `\\?`, and `\\'`.
- Fix bug with marshalling channels
- Add `div` for floored division
- Make `div` and `mod` variadic
- Support `bnot` for integer types.
- Define `(mod x 0)` as `x`
- Add `ffi/pointer-cfunction` to convert pointers to cfunctions