Enabled the link checker

Michael-F-Bryan · Michael-F-Bryan · commit 527a5cc5f636 · 2020-04-22T04:24:28.000+08:00
diff --git a/book/book.toml b/book/book.toml
@@ -3,3 +3,8 @@ authors = []
 language = "en"
 multilingual = false
 src = "src"
+
+[output.html]
+
+[output.linkcheck]
+follow-web-links = true
