[Stale Content] Archive or update M-13-13 supplemental guidance page — deadlines passed in 2013

## What needs to change
The supplemental guidance page for OMB M-13-13 was written to help agencies meet specific implementation deadlines that were due November 30, 2013. Those deadlines have long passed. The page is still linked from other resources so it should not be deleted, but it needs a prominent note added at the top clarifying it is a historical document.

## Where to find it
`pages/_resources/m-13-13-guidance.md`

## What to add
Add the following note at the very top of the page body, before any existing content:
```markdown
> **Note:** This supplemental guidance was published in 2013 to help agencies meet the initial implementation deadlines for OMB M-13-13. Those deadlines have passed. This page is maintained as a historical reference. For current open data policy guidance refer to the [Foundations for Evidence-Based Policymaking Act of 2018](https://resources.data.gov/categories/guidance/) and related OMB memoranda.
```

## How to verify
Visit the live page and confirm the historical note appears prominently at the top before any other content.