website: migrate to Hugo

### Is your feature request related to a problem? Please describe. The website [revive.run](https://revive.run/) was introduced 7 years ago in #74 and has not been actively maintained since. It is built with Gatsby (JS), and over time, has become difficult to maintain. In particular, ["Wrong URL to a rule description"](https://github.com/mgechev/revive.run/issues/58) is reported by users almost every month. The issue is not trivial to fix within the current stack and our knowledge. ### Describe the solution you'd like I propose migrating the website to [Hugo](https://gohugo.io/). Hugo is Go-based, simple to maintain, and well-suited for static documentation sites. It has proven effective for [Golangci-lint](https://golangci-lint.run/). I discussed this idea with @mgechev, and he agrees that Hugo would be a good fit for our needs. ### Describe alternatives you've considered We could continue maintaining the existing Gatsby-based website and fix issues (via vibecoding, since I'm not a JS expert).