Update CI badge and add GH workflow for documentation (#25)

Author: willhbr

.github/workflows/documentation.yml

@@ -0,0 +1,41 @@
+name: "Create API docs"
+on:
+  push:
+    branches: [master]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Crystal
+        uses: crystal-lang/install-crystal@v1
+
+      - name: Build
+        run: shards && crystal docs
+
+      - name: Upload
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ./docs
+
+  deploy:
+    if: github.event_name == 'push' && github.ref_name == github.event.repository.default_branch
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Deploy to Pages
+        id: deployment
+        uses: actions/deploy-pages@v2
+
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}

README.md

@@ -1,4 +1,4 @@
-# html_builder [![Build Status](https://travis-ci.org/crystal-lang/html_builder.svg)](https://travis-ci.org/crystal-lang/html_builder)
+# `html_builder` ![Build Status](https://github.com/crystal-lang/html_builder/actions/workflows/weekly.yml/badge.svg)
 
 DSL for creating HTML programatically (extracted from Crystal's standard library).