Update _index.md

[nestorayuso]

add Helium netID

Summary

Add NetID for Helium

Screenshots

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Changes

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Notes for Reviewers

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Checklist

• [ ] Scope: The referenced issue is addressed, there are no unrelated changes.
• [ ] Run Locally: Verified that the docs build using make server, posted screenshots, verified external links.
• [ ] Style Guidelines: Documentation obeys style guidelines in CONTRIBUTING.
• [ ] Commits: Commit messages follow guidelines in CONTRIBUTING, there are no fixup commits left.

[jpmeijers]

How about updating the table with all the latest assignments:

NetID Allocations_04272022.xlsx