chore(github-pages): improve doc on github-pages deployment

- add hint to use GitHub Actions GITHUB_REPOSITORY variable
- add paragraph how to get favicons working on a GitHub Pages deployment

closes nuxt#1776

Author: mhoffrog

content/3.deploy/github-pages.md

@@ -15,10 +15,20 @@ GitHub Pages only support static sites, Nuxt will pre-render your application to
 
 ::caution
 If you are **not** using a custom domain, you need to set `NUXT_APP_BASE_URL` to your repository-slug for your build step.
-
+:br
 **Example**: `https://<user>.github.io/<repository>/`: `NUXT_APP_BASE_URL=/<repository>/ npx nuxt build --preset github_pages`
 ::
 
+::tip
+**Zero Configuration ✨**
+:br
+In a **GitHub Workflow** you can make use of the pre-defined env var `GITHUB_REPOSITORY`: `NUXT_APP_BASE_URL="/${GITHUB_REPOSITORY##*/}/" npx nuxt build --preset github_pages`
+::
+
+::read-more{to="https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs#github-context" target="_blank"}
+Head over **GitHub Actions Context** to learn more about the GitHub Actions context variables.
+::
+
 ## Setup
 
 Follow the steps to [create a GitHub Pages site](https://docs.github.com/en/pages/getting-started-with-github-pages/creating-a-github-pages-site).
@@ -46,7 +56,8 @@ jobs:
           node-version: "20"
       # Pick your own package manager and build script
       - run: npm install
-      - run: npx nuxt build --preset github_pages
+      # Use NUXT_APP_BASE_URL="" if your GitHub Pages is configured for a custom domain
+      - run: NUXT_APP_BASE_URL="/${GITHUB_REPOSITORY##*/}/" npx nuxt build --preset github_pages
       - name: Upload artifact
         uses: actions/upload-pages-artifact@v3
         with:
@@ -74,3 +85,47 @@ jobs:
 ::read-more{to="https://nitro.unjs.io/deploy/providers/github-pages" target="_blank"}
 Head over **Nitro documentation** to learn more about the github-pages deployment preset.
 ::
+
+## Favicons
+
+Favicons typically are expected at hosting domain root. In case of a GitHub Pages deployment this does not work.
+
+For this reason favicon URLs should be defined for the pages header starting with the GitHub Pages base URL as absolute path to work for a single page app as well as for a multi-route app.
+
+::note
+Favicon files should be maintained within the projects `public/` folder.
+::
+
+**Example:** If you have `public/favicon.ico` and `public/favicon-16x16.png` your `nuxt.config.ts` should start as follows:
+```ts [nuxt.config.ts]
+// Make use of compile time environment var NUXT_APP_BASE_URL
+// to make baseURL work for GitHub Pages deployments as well.
+// See https://vite.dev/guide/env-and-mode.html for details.
+const baseURL = import.meta.env.NUXT_APP_BASE_URL
+  ? import.meta.env.NUXT_APP_BASE_URL
+  : "/";
+// https://nuxt.com/docs/api/configuration/nuxt-config
+export default defineNuxtConfig({
+  app: {
+    head: {
+      title: "My Nuxt App",
+      link: [
+        {
+          rel: "icon",
+          type: "image/x-icon",
+          href: baseURL + "favicon.ico?x=2",
+        },
+        {
+          rel: "icon",
+          type: "image/png",
+          sizes: "16x16",
+          href: baseURL + "favicon-16x16.png",
+        },
+        // Add more favicons if wanted ...
+      ],
+    },
+    // probale other app content ...
+  },
+  // other config ...
+)};
+```