chore: add release script + use 16:10 aspect ratio for plugin screenshots

release.sh: build, package ZIP, tag, and create GitHub release in one command.
Screenshot slots now use 16:10 (matches Steam Deck's 1280x800 screen) with
object-contain so full-screen Deck captures fit without cropping.

plugins/decky-vault/package.json

@@ -7,7 +7,8 @@
     "build": "rollup -c",
     "watch": "rollup -c -w",
     "build:zip": "rollup -c && ./scripts/build-zip.sh --no-build",
-    "zip": "./scripts/build-zip.sh"
+    "zip": "./scripts/build-zip.sh",
+    "release": "./scripts/release.sh"
   },
   "dependencies": {
     "@decky/api": "^1.1.3",