Add self-serve to docs

[matthewhelmke]

We are enabling users to sign up for Chainguard as customers themselves and are calling it "self-serve".

Because it will eventually cover many (all?) of our products, I have put the new page at the top of the product section of the documentation.

There will eventually be a need for images in the page, which requires that the page be in a directory, so that's how that happened.

This is rudimentary at the moment as the only way this can be done is via some new chainctl commands. This is also a pretty urgent request, so it isn't yet refined. This is truly the traditional open source MVP that will evolve and improve over time.

Fixes https://github.com/chainguard-dev/internal/issues/5842 but there will certainly be a newer issue created next week once Matthew meets with people working on the project and we move forward. This is baby step number one.

[netlify]

✅ Deploy Preview for ornate-narwhal-088216 ready!

Name	Link
🔨 Latest commit	9d43a70
🔍 Latest deploy log	https://app.netlify.com/projects/ornate-narwhal-088216/deploys/6a04538e36f0ac0008ae6f94
😎 Deploy Preview	https://deploy-preview-3317--ornate-narwhal-088216.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[matthewhelmke]

Page preview here: https://deploy-preview-3317--ornate-narwhal-088216.netlify.app/chainguard/self-serve/overview/