Publish the Raycast extension to the Raycast Store #21

Follow-up to #2.

The extension in raycast/ bundles the app, but it can't be published yet.

Scope

• raycast/swift/Package.swift depends on the app with .package(path: "../.."). Store extensions live in the raycast/extensions monorepo, so switch the dependency to .package(url: "https://github.com/janthoXO/KlangLadder", from: "<tag>") once the first release is tagged (GitHub release channel: unsigned zip of the app #3).
• Spike S2: ask Raycast whether the Store accepts an extension that installs a separate menu bar app with a login item.
• Set author in raycast/package.json to the real Raycast Store username, and add a LICENSE file (the manifest says MIT).
• Try the command inside Raycast (npm run dev). So far it was only tested by running the compiled bridge directly.
• Check whether a Store-installed extension's assets get the quarantine flag. If they do, the copied app would hit Gatekeeper.

Acceptance

• npm run publish opens a PR in raycast/extensions that builds in their CI.