Feat: activate always_modified plugin

plugins/always_modified/README.md

@@ -0,0 +1,14 @@
+# Always Modified
+
+Say you want to sort by modified date/time in a theme template, but not all
+your articles have modified date/timestamps explicitly defined in article
+metadata. This plugin facilitates that sorting by assuming the modified date
+(if undefined) is equal to the created date.
+
+## Usage
+
+1. Add `ALWAYS_MODIFIED = True` to your settings file.
+2. Now you can sort by modified date in your templates:
+
+    {% for article in articles|sort(reverse=True,attribute='modified') %}
+