Add support for SonarLint

**Name:** SonarLint
**URL:** https://www.sonarsource.com/products/sonarlint/

SonarLint is not working out-of-the-box with ALE. Therefore, I have made some investigation and even a simple prototype to make it work: https://github.com/burrima/sonarlint-ls-wrapper (works with C++ and Python).

There was also some prior discussion taking place on the Sonar community forum: https://community.sonarsource.com/t/running-sonarlint-language-server-from-shell/24440

I don't think this is purely an ALE issue, SonarLint should also get some "fixes". ALE is generally not supporting all features of the LSP protocol. Most importantly, it does not expect requests sent actively by the language server. On the other side, SonarLint is using some proprietary features, which is also not nice. There is no possibility in ALE (at least not from what I've seen) to reply to these proprietary requests (e.g. by linter integration script).

Would be nice to hear from you (the maintainers of ALE) if you generally like the idea of integrating SonarLint. I am also reaching out to the SonarLint developers with the goal to enable a collaboration between people of both projects - if there is interest from both sides.