Add sentence how to run *.http files (#2221)

For users new to VSCode it may not be obvious how to run *.http files.

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Co-authored-by: René Jeglinsky <rene.jeglinsky@sap.com>

Author: modood-alvi

get-started/in-a-nutshell.md

@@ -781,7 +781,7 @@ Books book = persistenceService.run(byId).single(Books.class);
 
 ### Sample HTTP Requests
 
-Test the implementation by submitting orders until you see the error messages. Create a file called _test.http_ and copy the request into it.
+Test the implementation by submitting orders until you see the error messages. Create a file called _test.http_ and copy the request into it. Send requests from your IDE supporting `*.http` files with, for example, a [REST Client](/tools/cds-editors#add-useful-plugins).
 
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