Add deprecation notice

Author: OrKarstoft

README.md

@@ -1,5 +1,8 @@
 # github-releasediff
 
+> [!IMPORTANT]
+> This library is no longer maintained and is archived. It will eventually be deleted.
+
 Simple go package to get number of releases between two releases.
 
 The github client used is [google/go-github](https://github.com/google/go-github)
@@ -28,4 +31,4 @@ fmt.Printf("%v\n", resp.Rate)
 // Output:
 // There are 2 releases between v2.0.2 and v2.1.0
 // github.Rate{Limit:5000, Remaining:4685, Reset:github.Timestamp{2020-10-07 09:30:12 +0200 CEST}}
-```
+```