Add documentation on how to find model parameters for leader model in AutoML

[exalate-issue-sync]

This seems like a popular question on StackOverflow, so let's add something about this to the docs: https://stackoverflow.com/questions/55081358/how-to-find-best-params-of-leader-model-in-automl-h2o-python/55083154#55083154

I think a good location for this in in the AutoML Output section, after Leaderboard: http://docs.h2o.ai/h2o/latest-stable/h2o-docs/automl.html#automl-output

Example should include both an R & Python example like the other code examples.

[h2o-ops]

JIRA Issue Details

Jira Issue: PUBDEV-8179
Assignee: Erin LeDell
Reporter: Erin LeDell
State: Resolved
Fix Version: 3.34.0.1
Attachments: N/A
Development PRs: Available

[h2o-ops]

Linked PRs from JIRA

#5669