readme: adds note about upgrading to v3

proxycrawl · proxycrawl · commit e4a1bd387c8d · 2020-12-21T12:47:26.000+08:00
diff --git a/README.md b/README.md
@@ -15,6 +15,10 @@ Then import the CrawlingAPI, ScraperAPI, etc as needed.
 from proxycrawl import CrawlingAPI, ScraperAPI, LeadsAPI
 ```
 
+### Upgrading to version 3
+
+Version 3 deprecates the usage of ProxyCrawlAPI in favour of CrawlingAPI (although is still usable). Please test the upgrade before deploying to production.
+
 ## Crawling API
 
 First initialize the CrawlingAPI class.
