HPCC-10029 Add Dictionary Example to ECL Playground

Fixes HPCC-10029

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #5026 from GordonSmith/HPCC-10029

HPCC-10029 Add Dictionary Example to ECL Playground

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>