Enable linting of Typescript files for static-site [#905]

Load up required bits of ESLint machinery; update the
`lint:static-site` script to also look at *.tsx? files.

package.json

@@ -15,7 +15,7 @@
     "build": "./build.sh",
     "lint": "npm run lint:server",
     "lint:server": "DEBUG=eslint:cli-engine npx eslint --ext .js,.jsx .",
-    "lint:static-site": "cd static-site && DEBUG=eslint:cli-engine npx eslint --ext .js,.jsx .",
+    "lint:static-site": "cd static-site && DEBUG=eslint:cli-engine npx eslint --ext .js,.jsx,.ts,.tsx .",
     "server": "node server.js",
     "groups": "node server.js --app ./src/groupsApp.js",
     "start": "npm run server",

static-site/.eslintrc.yaml

@@ -1,10 +1,16 @@
 # Prevent parent configuration from being applied.
 root: true
 
+plugins:
+  - "@typescript-eslint"
+
+parser: "@typescript-eslint/parser"
+
 extends:
   - eslint:recommended
   - plugin:react/recommended
   - plugin:react-hooks/recommended
+  - plugin:@typescript-eslint/recommended
   # We use the recommended Next.js eslint configuration `next/core-web-vitals` as per
   # <https://nextjs.org/docs/pages/building-your-application/configuring/eslint#core-web-vitals>
   # As of April 2024, the extension simply adds the `@next/next/core-web-vitals` plugin: