HPCC-8872 DOCS:ECL Watch Docs

Fix HPCC-8872 DOCS:ECL Watch Docs
Document the new ECL Watch.
ReBased on to 5.0 and new images added
Post Plygrd split off different branch.(merged 6166)
First  POST MERGE/REBASE commit.

Signed-off-by: g-pan <greg.panagiotatos@lexisnexis.com>
Merge pull request #6192 from g-pan/HPCC-8872-ECLWatch5.0

HPCC-8872 DOCS:ECL Watch Docs

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>