Syntax error in watchdog

[myndzi]

https://github.com/tapjs/foreground-child/blob/main/src/watchdog.ts#L25

There's an extra ) in the code, so the watchdog process never successfully spawns. I was going to send a PR, but I don't quite understand the full intentions of this library. It's surprising to me that the tests don't catch this, so I got a bit lost when trying to decide how to write a test that will fail here and succeed when the typo is fixed.

Beyond that, there should probably be some defined behavior for if the watchdog exits unexpectedly - for example, kill the child, since the watchdog is incapable of doing its job - but that's a design decision best left to y'all.