fix: Generate d.ts for dev tools so plugins can use it (#17019)

Author: Artur-

vaadin-dev-server/package.json

@@ -12,6 +12,7 @@
     "@koa/cors": "^4.0.0",
     "@open-wc/dev-server-hmr": "^0.1.2-next.0",
     "@open-wc/testing": "^3.1.7",
+    "@rollup/plugin-typescript": "^11.1.1",
     "@types/chai": "^4.3.4",
     "@types/sinon": "^10.0.13",
     "@web/dev-server": "^0.1.35",
@@ -20,6 +21,7 @@
     "@web/test-runner-playwright": "^0.9.0",
     "prettier": "^2.8.4",
     "sinon": "^15.0.1",
+    "tslib": "^2.5.3",
     "vite": "^4.1.4"
   },
   "dependencies": {

vaadin-dev-server/tsconfig.json

@@ -19,5 +19,10 @@
     "skipLibCheck": true,
     "baseUrl": ".",
     "esModuleInterop": true,
-  }
+    "declaration": true,
+    "declarationDir": "src/main/resources/META-INF/frontend/vaadin-dev-tools",
+    "emitDeclarationOnly": true
+  },
+  "include": ["frontend/vaadin-dev-tools.ts"],
+  "exclude": []
 }

vaadin-dev-server/vite.config.js

@@ -1,5 +1,6 @@
 import { fileURLToPath } from 'url';
 import { defineConfig } from 'vite';
+import typescript from '@rollup/plugin-typescript';
 
 export default defineConfig({
   build: {
@@ -15,6 +16,7 @@ export default defineConfig({
         // Ensure consistent file name for dev tools bundle
         entryFileNames: 'vaadin-dev-tools.js'
       },
+      plugins: [typescript({ tsconfig: './tsconfig.json' })],
       // Do not resolve the following imports, these modules
       // will be provided by the application that hosts the dev tools.
       external: [