Add support for Semgrep

**Name:** Semgrep
**URL:** https://github.com/returntocorp/semgrep

Hi there,

I'm hoping to add Semgrep support to ALE. Semgrep is a relatively new, multilingual, static analysis tool. Documentation can be found [here](https://semgrep.dev/docs/). I'd be happy to create a PR and add support myself. I have one question: is there anything special about adding a multilingual tool, or is there an existing multilingual tool integration I can look at to get started?