Update project typecheck configuration

Update project typecheck configuration so that typechecking may be
additionally applied to the `dev-server` area of the project. This helps
for typechecking usage of components in the "UI Playground" app.

* Add `tsconfig.json` for `dev-server` area of project
* Add "project references" at root level
  See https://www.typescriptlang.org/docs/handbook/project-references.html
* Update `package.json` `typecheck` script

dev-server/tsconfig.json

+{
+  "compilerOptions": {
+    "allowJs": true,
+    "checkJs": true,
+    "lib": ["es2018", "dom"],
+    "jsx": "react-jsx",
+    "jsxImportSource": "preact",
+    "module": "commonjs",
+    "noEmit": true,
+    "strict": true,
+    "noImplicitAny": false,
+    "target": "ES2020"
+  },
+  "include": ["ui-playground/**/*.js"]
+}

dev-server/ui-playground/components/PatternPage.js

@@ -91,7 +91,7 @@ export function PatternExamples({ children, title }) {
     <table className="PatternExamples">
       {title && (
         <tr>
-          <th colSpan="3">
+          <th colSpan={3}>
             <h3>{title}</h3>
           </th>
         </tr>

dev-server/ui-playground/components/PlaygroundApp.js

@@ -54,7 +54,7 @@ export default function PlaygroundApp() {
               <a
                 className="PlaygroundApp__nav-link"
                 key={c.route}
-                href={c.route}
+                href={/** @type string */ (c.route)}
                 onClick={e => navigate(e, c.route)}
               >
                 {c.title}

dev-server/ui-playground/components/patterns/MenuPatterns.js

@@ -15,7 +15,7 @@ export default function MenuPatterns() {
         <p>A simple Menu usage example</p>
         <PatternExamples>
           <PatternExample details="Menu">
-            <Menu label="Edit">
+            <Menu title="Example Menu" label="Edit">
               <MenuItem label="Zoom in" />
               <MenuItem label="Zoom out" />
               <MenuItem label="Undo" />

dev-server/ui-playground/index.js

@@ -7,4 +7,4 @@ import sidebarIcons from '../../src/sidebar/icons';
 registerIcons(sidebarIcons);
 
 const container = document.querySelector('#app');
-render(<PlaygroundApp />, container);
+render(<PlaygroundApp />, /** @type Element */ (container));

package.json

@@ -127,7 +127,7 @@
     "checkformatting": "prettier --check '**/*.{js,scss}'",
     "format": "prettier --list-different --write '**/*.{js,scss}'",
     "test": "gulp test",
-    "typecheck": "tsc --build src/tsconfig.json",
+    "typecheck": "tsc --build tsconfig.json",
     "report-coverage": "codecov -f coverage/coverage-final.json",
     "version": "make clean build"
   }

tsconfig.json

+{
+  "references": [{ "path": "src/" }, { "path": "dev-server/" }],
+  "files": []
+}