Return renderer state from pop()

[aryashi100]

Addresses a renderer contract mismatch noted in code comments.

Changes:

• Updated p5.Renderer.pop() to return the restored renderer style after state restoration.
• Aligns implementation with comments in p5.Renderer2D.js that describe the expected renderer contract.
• Note: While running the test suite locally, one existing documentation test for loadFont (example Rhino test #4) failed. This appears unrelated to the renderer change and was present prior to this modification.

Screenshots of the change:
N/A (code-only change)

PR Checklist

• npm run lint passes
• Inline reference is included / updated (not applicable)
• Unit tests are included / updated (not applicable)