Add missing link to core concepts documentation.

See spring-projects/spring-data-commons#3463

Author: mp911de

src/main/antora/modules/ROOT/pages/repositories.adoc

@@ -3,6 +3,6 @@
 :page-section-summary-toc: 1
 
 This chapter explains the basic foundations of Spring Data repositories and MongoDB specifics.
-Before continuing to the MongoDB specifics, make sure you have a sound understanding of the basic concepts.
+Before continuing to the MongoDB specifics, make sure you have a sound understanding of the basic concepts explained in xref:repositories/core-concepts.adoc[Working with Spring Data Repositories].
 
 The goal of the Spring Data repository abstraction is to significantly reduce the amount of boilerplate code required to implement data access layers for various persistence stores.