remove brew

.github/workflows/github-pages.yml

@@ -12,18 +12,12 @@ jobs:
       id-token: write
     environment: github-pages
     runs-on: ubuntu-latest
+    container: alpine
     steps:
       - uses: actions/checkout@v4
-      - uses: Homebrew/actions/setup-homebrew@master
-      - id: brew_cache
-        run: echo "::set-output name=dir::$(brew --cache)"
-      - uses: actions/cache@v3
-        with:
-          path: ${{ steps.brew_cache.outputs.dir }}
-          key: brew-v3
       - name: Build
         run: |
-          brew bundle
+          apk add mdbook
           mdbook build
       - uses: actions/upload-pages-artifact@v2
         with:

Brewfile

@@ -1 +0,0 @@
-brew "mdbook"

README.md

@@ -4,14 +4,12 @@
 
 ### 前提
 
-- Ubuntu 20.04 LTS
-- Homebrew
+- mdBook
 
 ### 手順
 
 下記のコマンドを実行すると `book` ディレクトリ以下にファイルが生成されます。
 
 ```sh
-brew bundle
 mdbook build
 ```