chore(gitignore): add git blacklist

SangKa · SangKa · commit ccfa2ba12818 · 2018-05-06T15:15:50.000+08:00
diff --git a/.gitignore b/.gitignore
@@ -38,3 +38,9 @@ jspm_packages
 
 ./code/node_modules
 ./code/*.log
+
+# GitBook
+_book
+*.pdf
+*.epub
+*.mobi
