Update README to specify last two months for stats

Clarified the time frame for page opening statistics.

Author: mrflos

docs/en/README.md

@@ -1,6 +1,6 @@
 # Extension stats
 
-This extension allows to follow how many times a page has been opened. 
+This extension allows to follow how many times a page has been opened the last two months. 
 
 ## Activate the extension
 
@@ -13,4 +13,4 @@ Then, all opened page is followed.
  - You have to create a new page being connected as administrator.
  - When editing the new page, use the button `components` and click on `statistic` into `management` part.
 It will insert the action `{{stats}}` into the new page.
- - Save and use the interface to see `statistics`.
+ - Save and use the interface to see `statistics`.