Replace Vercel with GitHub pages

This requires additional changes in the repository GitHub Pages
settings. _Source_ needs to be set to _GitHub Actions_, and a custom
domain needs to be configured.

.github/workflows/website.yml

@@ -0,0 +1,25 @@
+name: website
+on:
+  push:
+    branches: [main]
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pages: write
+      id-token: write
+    environment:
+      name: Website
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v3
+        with: {node-version: 18}
+      - run: npm ci
+      - run: npm run docs
+      - uses: actions/upload-pages-artifact@v2
+        with:
+          path: public
+      - uses: actions/deploy-pages@v2
+        id: deployment

package.json

@@ -120,7 +120,6 @@
     "build": "tsc --build --clean && tsc --build && type-coverage",
     "docs": "npm run docs-prep && npm run docs-generate && npm run docs-post",
     "docs-css": "postcss --output public/index.css docs/_asset/index.css",
-    "docs-deploy": "vercel && vercel alias $(pbpaste) mdxjs.com && vercel alias $(pbpaste) www.mdxjs.com",
     "docs-generate": "cross-env NODE_LOADER_CONFIG=website/loader.js node --no-warnings --loader @node-loader/core website/generate.js",
     "docs-js": "npm run docs-js-default && npm run docs-js-editor",
     "docs-js-default": "esbuild --bundle --conditions=browser,production --define:process.env.NODE_ENV=\\\"production\\\" --log-level=warning --minify --outfile=public/index.js --target=es2020 docs/_asset/index.js",

website/prep.js

@@ -75,31 +75,6 @@ await pAll(
 
 console.log('✔ %d redirects', Object.keys(redirect).length)
 
-// To do: drop Vercel.
-/** @type {Array<Readonly<Redirect>>} */
-const vercelRedirects = []
-/** @type {string} */
-let redirectFrom
-
-for (redirectFrom in redirect) {
-  if (Object.hasOwn(redirect, redirectFrom)) {
-    const source = redirectFrom.replace(/\/index.html$/, '/')
-    const destination = redirect[redirectFrom]
-    vercelRedirects.push({destination, source})
-  }
-}
-
-// To do: drop Vercel.
-/** @type {Record<string, unknown> & {redirects: ReadonlyArray<Readonly<Redirect>>}} */
-const vercelInfo = JSON.parse(String(await fs.readFile('vercel.json')))
-await fs.writeFile(
-  'vercel.json',
-  JSON.stringify({...vercelInfo, redirects: vercelRedirects}, undefined, 2) +
-    '\n'
-)
-
-console.log('✔ `vercel.json` redirects')
-
 /**
  *
  * @param {string} to