Modernize ActiveMQ website: migrated to Hugo

[kenliao94]

This PR modernize the existing ActiveMQ website in two different dimensions:

• It migrates to Hugo to do the static site generation
• It modifies the UI to use more modern looking fonts and style, while keeping a similar layout and same URLs

[jbonofre]

That's great ! Thanks a lot @kenliao94 !

As discussed, I agree with the plan:

1. Use Hugo with the same content
2. Some update on the look'n feel
3. An iterating large effort to update the content and use versioned documentation

Some notes about this PR:

1. I would update the README.md file to provide instruction for Hugo (build, test, publication), including using Hugo Docker image.
2. AGENTS.md seems not directly related to this PR, but I'm fine to include it there. I guess you used AI to assist you there. That makes perfect sense.
3. In support.md, I have issues about the duplicate url: content.
4. hugo/.hugo_build.lock should not be in the PR (local build environment file). It should be added to the .gitignore.
5. The layout doesn't render nicely on my browser. I'm investigating why.

I will do a larger review later today/tomorrow.