Theme: Add /theme-playground route (#111974)

* add basic theme-playground page

* basic theme playground

* generate schema

* sort of include the schema

* proper json schema

* add base theme

* bit of tidy up

* don't use appEvents.emit

* tidy up ThemeDemo

* extract translations

* add CODEOWNERS

package.json

@@ -62,7 +62,8 @@
     "stats": "webpack --mode production --config scripts/webpack/webpack.prod.js --profile --json > compilation-stats.json",
     "storybook": "yarn workspace @grafana/ui storybook --ci",
     "storybook:build": "yarn workspace @grafana/ui storybook:build",
-    "themes-generate": "esbuild --target=es6 ./scripts/cli/generateSassVariableFiles.ts --bundle --platform=node --tsconfig=./scripts/cli/tsconfig.json | node",
+    "themes-schema": "typescript-json-schema ./tsconfig.json NewThemeOptions --include 'packages/grafana-data/src/themes/createTheme.ts' --out public/app/features/theme-playground/schema.generated.json",
+    "themes-generate": "yarn themes-schema && esbuild --target=es6 ./scripts/cli/generateSassVariableFiles.ts --bundle --platform=node --tsconfig=./scripts/cli/tsconfig.json | node",
     "themes:usage": "eslint . --ignore-pattern '*.test.ts*' --ignore-pattern '*.spec.ts*' --cache --plugin '@grafana' --rule '{ @grafana/theme-token-usage: \"error\" }'",
     "typecheck": "tsc --noEmit && yarn run packages:typecheck",
     "plugins:build-bundled": "echo 'bundled plugins are no longer supported'",
@@ -255,6 +256,7 @@
     "ts-jest": "29.4.0",
     "ts-node": "10.9.2",
     "typescript": "5.9.2",
+    "typescript-json-schema": "^0.65.1",
     "webpack": "5.101.0",
     "webpack-assets-manifest": "^5.1.0",
     "webpack-cli": "6.0.1",