Widgets: Add TypeScript project config (WordPress#78467)

* add TypeScript project config for widgets/

resolve @wordpress/*, CSS module imports, and JSX in widget .tsx files

* document widget package.json in wp-build README

list it in the widgets Structure tree as an optional npm dependencies manifest

* add widgets to root tsconfig references

ensures CI type-checks widgets via tsgo --build

Author: retrofox

packages/wp-build/README.md

@@ -549,6 +549,7 @@ widgets/
     widget.ts       # Runtime schema entry point (optional)
     render.tsx      # UI component entry point (optional)
     render.scss     # Optional styles (bundled inline when imported from render.tsx)
+    package.json    # Optional npm dependencies manifest
 ```
 
 ### Why two entries?

tsconfig.json

@@ -93,7 +93,8 @@
 		{ "path": "storybook" },
 		{ "path": "test/e2e" },
 		{ "path": "test/storybook-playwright" },
-		{ "path": "test/performance" }
+		{ "path": "test/performance" },
+		{ "path": "widgets" }
 	],
 	"files": []
 }

widgets/tsconfig.json

@@ -0,0 +1,14 @@
+{
+	"$schema": "https://json.schemastore.org/tsconfig.json",
+	"extends": "../tsconfig.base.json",
+	"compilerOptions": {
+		"jsx": "react-jsx",
+		"rootDir": ".",
+		"noEmit": true,
+		"emitDeclarationOnly": false,
+		"composite": false,
+		"types": [ "style-imports" ]
+	},
+	"include": [ "**/*.ts", "**/*.tsx" ],
+	"exclude": [ "**/test/**", "build", "node_modules" ]
+}