specify module name kotest-assertions-json (#3898)

Added import instructions to doc. Not impossible to guess the full
module name, but the docs should make it explicit. Some other modules
are missing this too.

---------

Co-authored-by: Emil Kantis <[email protected]>

Author: jlous

documentation/docs/assertions/json/overview.md

@@ -4,6 +4,8 @@ slug: json-overview.html
 sidebar_label: Overview
 ---
 
+To use these matchers add `testImplementation("io.kotest.extensions:kotest-assertions-json:<version>")` to your build.
+
 ## Basic matchers
 
 | Matcher              | Description                                        | Targets       |

documentation/versioned_docs/version-5.8/assertions/json/overview.md

@@ -4,6 +4,8 @@ slug: json-overview.html
 sidebar_label: Overview
 ---
 
+To use these matchers add `testImplementation("io.kotest.extensions:kotest-assertions-json:<version>")` to your build. 
+
 ## Basic matchers
 
 | Matcher              | Description                                        | Targets       |