CI: pip install prettytable

.github/workflows/book.yml

@@ -39,6 +39,7 @@ jobs:
             - name: Install ghp-import and mdbook
               run: |
                 pip install ghp-import
+                pip install prettytable
                 sudo apt -y install make wget
                 wget "https://github.com/badboy/mdbook-toc/releases/download/0.11.2/mdbook-toc-0.11.2-x86_64-unknown-linux-gnu.tar.gz"
                 wget "https://github.com/lzanini/mdbook-katex/releases/download/v0.4.1/mdbook-katex-v0.4.1-x86_64-unknown-linux-gnu.tar.gz"