Added `round` up documentation

[JaydeepGo]

Summary

In the Nunjucks package, we have functionality to round up with round filter but it was not mentioned in the documentation. I have Added round up in the documentation.

Checklist

I've completed the checklist below to ensure I didn't forget anything. This makes reviewing this PR as easy as possible for the maintainers. And it gets this change released as soon as possible.

• [x] Proposed change helps towards purpose of this project.
• [x] Documentation is added / updated to describe proposed change.
• [x] Tests are added / updated to cover proposed change.
• [x] Changelog has an entry for proposed change (if user-facing fix or feature).

[JaydeepGo]

Hi @ogonkov, Thanks for PR approval. I am not getting the option to merge. Is there anything else I need to do?

[ogonkov]

Yep, get approve from repo maintainer )

[JaydeepGo]

Thanks for the info.