Migrate CI from Travis to GitHub Actions (#46)

Travis CI is no longer running for this repo. Replace .travis.yml with
an equivalent GitHub Actions workflow that builds the Hugo site (with
the grunt content-index step) and pushes the rendered output to the
master branch via peaceiris/actions-gh-pages. Hugo version, build steps,
and target branch are unchanged so GitHub Pages keeps serving from the
same place. README badge updated to point at the new workflow.

Author: rumblefrog

.github/workflows/deploy.yml

@@ -0,0 +1,55 @@
+name: Build and Deploy
+
+on:
+  push:
+    branches:
+      - src
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+concurrency:
+  group: pages-deploy
+  cancel-in-progress: false
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    env:
+      HUGO_VERSION: 0.88.1
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: true
+          fetch-depth: 0
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: lts/*
+
+      - name: Setup Hugo
+        uses: peaceiris/actions-hugo@v3
+        with:
+          hugo-version: ${{ env.HUGO_VERSION }}
+
+      - name: Install dependencies
+        run: |
+          npm install -g grunt-cli yarn
+          yarn set version latest
+          yarn install --no-lockfile
+
+      - name: Build content index
+        run: grunt content-index
+
+      - name: Build site
+        run: hugo --minify
+
+      - name: Deploy to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v4
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./public
+          publish_branch: master

.travis.yml

@@ -1,4 +1,4 @@
-# SourceBans++ Website [![Travis branch](https://img.shields.io/travis/sbpp/sbpp.github.io/src.svg?style=flat-square)](https://travis-ci.org/sbpp/sbpp.github.io)
+# SourceBans++ Website [![Build and Deploy](https://github.com/sbpp/sbpp.github.io/actions/workflows/deploy.yml/badge.svg?branch=src)](https://github.com/sbpp/sbpp.github.io/actions/workflows/deploy.yml)
 
 ### Adding Articles