Update `NOTICE.md` to include the `keystone-hello-world` template

[lex57ukr]

Goal

Ensure NOTICE.md accurately reflects all Keystone templates maintained by the project, including the keystone-hello-world template.

Scope

• Review the current contents of NOTICE.md
• Add a reference to the keystone-hello-world template
• Ensure formatting and ordering are consistent with existing entries
• Confirm no duplicate or outdated references remain
• Verify that the man page references remain accurate and up to date

Outcome

• NOTICE.md fully and accurately documents all maintained Keystone templates
• Users can discover the keystone-hello-world template through project documentation

Notes

This is a documentation-only change and does not affect runtime behavior.

[lex57ukr]

Triage

Scope clarification

This is a documentation-only change.

• Update NOTICE.md to include the keystone-hello-world template:
  https://github.com/knight-owl-dev/keystone-hello-world
• Ensure formatting and ordering are consistent with existing entries
• Verify there are no duplicate or outdated references

Notes

• No code or tooling changes expected
• No tests required
• A single small PR is sufficient