[doc] update documentation to v2

README.md

@@ -6,7 +6,7 @@ Colly provides a clean interface to write any kind of crawler/scraper/spider.
 
 With Colly you can easily extract structured data from websites, which can be used for a wide range of applications, like data mining, data processing or archiving.
 
-[![GoDoc](https://godoc.org/github.com/gocolly/colly?status.svg)](https://godoc.org/github.com/gocolly/colly)
+[![GoDoc](https://godoc.org/github.com/gocolly/colly?status.svg)](https://pkg.go.dev/github.com/gocolly/colly/v2)
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