feat(feel): Add new built-in function

[lzgabel]

Description

Extend the FEEL documentation with the following new built-in function:

• Add partition function that allows to partitioning of collections in an easy way feel-scala#881

When should this change go live?

• This is a bug fix, security concern, or something that needs urgent release support.
• This is already available but undocumented and should be released within a week.
• This on a specific schedule and the assignee will coordinate a release with the DevEx team. (apply hold label or convert to draft PR)
• This is part of a scheduled alpha or minor. (apply alpha or minor label)
• There is no urgency with this change and can be released at any time.

PR Checklist

• My changes are for an already released minor and are in /versioned_docs directory.
• My changes are for the next minor and are in /docs directory (aka /next/).
• My changes require an Engineering review
• My changes require a technical writer review

[CLAassistant]

All committers have signed the CLA.

[lzgabel]

👋 Hi @saig0, @christinaausley. Please take a moment to review this feature. 🙇

[akeller]

Since this is an external contribution, we can review and accept this PR, then backport changes in a separate PR.

[christinaausley]

Once @saig0 has approved, I will merge this and backport in a separate PR 👍

[saig0]

LGTM. 🚀

[saig0]

@christinaausley there is no need to backport the PR. The new function is only available in the next version (8.7).