docs: add PV feature deprecation note

close #682

Author: cotes2020

_posts/2021-01-03-enable-google-pv.md

@@ -6,6 +6,8 @@ categories: [Blogging, Tutorial]
 tags: [google analytics, pageviews]
 ---
 
+> The content of this post applies only to [_Universal Analytics property_](https://support.google.com/analytics/answer/10220206) (UA), not [_Google Analytics 4_](https://support.google.com/analytics/answer/10089681) (GA 4). In addition, since [UA is about to be deprecated on Jul 1, 2023](https://support.google.com/analytics/answer/11583528), the Page Views feature of [_Chirpy_][chirpy-homepage] will also be deprecated at that time.
+{: .prompt-danger }
 
 This post is to enable Page Views on the [**Chirpy**][chirpy-homepage] theme based blog that you just built. This requires technical knowledge and it's recommended to keep the `google_analytics.pv.*` empty unless you have a good reason. If your website has low traffic, the page views count would discourage you to write more blogs. With that said, let's start with the setup.