goobook: add page (#9356)

pages/linux/goobook.md

@@ -0,0 +1,12 @@
+# goobook
+
+> Access Google contacts from `mutt` or the command line.
+> More information: <https://manned.org/goobook>.
+
+- Allow `goobook` to access Google contacts using OAuth2:
+
+`goobook authenticate`
+
+- Dump all contacts to XML (stdout):
+
+`goobook dump_contacts`