Add post_revision plugin as submodule

.gitmodules

@@ -106,3 +106,6 @@
 [submodule "ga_page_view"]
 	path = ga_page_view
 	url = https://github.com/jhshi/pelican.plugins.ga_page_view.git
+[submodule "post_revision"]
+	path = post_revision
+	url = https://github.com/jhshi/pelican.plugins.post_revision

post_revision

@@ -0,0 +1 @@
+Subproject commit a511ab06b7fca1827c5f7e6c5cdf991710fbd7cb