release: Add initial v0.1.0-alpha release metadata

[NAME-ASHWANIYADAV]

Type of change

• 🐛 Bug fix
• 🚀 New feature / enhancement
• 📖 Documentation
• ⚙️ CI / tooling
• ⚠️ Breaking change

What this PR does

Prepares the first v0.1.0-alpha release of the Agones Headlamp plugin so it can be published to ArtifactHub and appear in Headlamp's Plugin Catalog, as discussed with @illume. It mirrors the structure of the Kmesh release PR (headlamp-k8s/plugins#985):

• 0.1.0-alpha/artifacthub-pkg.yml — ArtifactHub package metadata: display name, Agones logo, description, changelog entries for everything shipped so far (Overview dashboard, Fleet/GameServer/FleetAutoscaler views, allocation dialog, map view, CRD detection guard, Allocated-state banner), plus the plugin archive URL and SHA256 checksum annotations.
• 0.1.0-alpha/README.md — release README for the catalog listing: key features, prerequisites, installation via the Plugin Catalog, and local development setup.
• package.json — version bumped 0.1.0 → 0.1.0-alpha, and the scaffold description ("Your Headlamp plugin") replaced with a real one.
• package-lock.json — root version synced so npm ci stays green in CI.

Test plan

Automated checks

• npm ci
• npm run build
• npm run tsc
• npm run lint
• npm run format -- --check
• npm run test

Manual verification

No runtime code changes — this PR only adds release metadata and bumps the package version. The release tarball was built locally with npm run package from this branch.

Notes for reviewers

• Release asset required: the archive-url annotation points to
  https://github.com/agones-dev/headlamp-plugin/releases/download/v0.1.0-alpha/agones-plugin-0.1.0-alpha.tar.gz.
  When creating the v0.1.0-alpha tag/release, the exact tarball matching the checksum in artifacthub-pkg.yml
  (SHA256:7b2c3141e72538d773cbd91ea82490d391ee07132bb01c184620346f2b02af09) needs to be uploaded as the release asset — I can share the built tarball, or we can regenerate it and update the checksum in this PR before merge.
• ArtifactHub registration: for the plugin to show up in the catalog, this repository also needs to be registered on ArtifactHub as a Headlamp plugins repo (maintainer-side, one-time step).
• Happy to move the 0.1.0-alpha/ directory elsewhere (e.g. under an artifacthub/ folder) if you prefer a different layout.

[markmandel]

I think you read my mind. I was just thinking about talking to you about doing something like this! ☺️

[NAME-ASHWANIYADAV]

Perfect timing then! 😄 Let me know if you have any feedback on this.
(P.S. Could you please approve the CI workflow run when you have a moment?)

[illume]

@NAME-ASHWANIYADAV LGTM

Do you have the tar.gz file it generated? You'll need to attach that to the release when it's done.

[NAME-ASHWANIYADAV]

@illume PTAL !!

[NAME-ASHWANIYADAV]

@illume please re-review !!

[illume]

Please rebase against main to remove the merge main commits

[NAME-ASHWANIYADAV]

@illume will appreciate a re-review !!

[markmandel]

Once this lands - would be great to have a blog post on https://agones.dev/site/blog/ !

We can also forward that content to the mailing list, and link to it from slack as well 👍🏻

[NAME-ASHWANIYADAV]

@illume Just a gentle ping on this!
The rebase is done.
Let me know if it looks good to approve now
@markmandel - I love the blog post idea, definitely up for it once this is out !!!!!!