Make sentry an optional dependency #155

https://sqlfum.pt/ recently switched to a wasm-compiled implementation. It's 50MB, which, even gzip compressed, is big and slow for browsers to process. Compiling with tinygo fails because sentry-go depends on some stdlib things that tinygo doesn't support. Is it possible to have some tags to opt-out or opt-in to sentry? I'd like to make sqlfmt faster and smaller, and this is one thing that could help.