[DOC] Multi-terms documentation - Add to example missing, size and order

[zvischutz]

What do you want to do?

• [ ] Request a change to existing documentation
• [X] Add new documentation
• [ ] Report a technical problem with the documentation
• [ ] Other

Tell us about your request. Provide a summary of the request and all versions that are affected. I encountered an issue where I had to use multi_terms aggregation with missing. I did not see in the documentation that this possibility exists. Lucky to me I just guessed and tried and it worked ! Can you mention it on the documentation or add it to the example you described there.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

[hdhalter]

Thanks for entering the issue, @zvischutz ! Do you want to take a stab at creating a PR? We have information about how to contribute here: https://github.com/opensearch-project/documentation-website/blob/main/CONTRIBUTING.md.