Fix link purl_searcher -> purls_searcher

Author: JanHoefelmeyer

examples/README.md

@@ -3,4 +3,4 @@
 A currenty very short list how to use `github.com/csaf-poc/csaf_distribution` as a library.
 As the API is currently WIP these are are likely to be modified or extented.
 
-* [purl_searcher](./purl_searcher/main.go) is a tool to search for PURLs in local advisories by given product IDs.
+* [purls_searcher](./purls_searcher/main.go) is a tool to search for PURLs in local advisories by given product IDs.