Add default label `S-needs-triage` to issues

Add label `S-needs-triage` to issue template.

**Additional context**
`S-needs-triage` label is an indication to devs that this issue is from an external contributor and has not yet been read by any other dev on the team.

Ref https://github.com/paradigmxyz/reth/blob/28d52312acd46be2bfc46661a7b392feaa2bd4c5/.github/ISSUE_TEMPLATE/feature.yml?plain=1#L3

Inspect the repository's .github/ISSUE_TEMPLATE files and compare them with the referenced reth feature.yml example. Add S-needs-triage as the default label for the relevant issue template, then verify the template configuration and confirm that a newly created issue receives the label.

Written by the indexing model from the issue text.