Improve WebGL font error message to suggest textFont() usage

[yugalkaushik]

Improves the error message when rendering text in WebGL mode without properly setting a font.

Problem:
The current error "only Opentype (.otf) and Truetype (.ttf) fonts are supported" is misleading when users have loaded a valid font but forgot to call textFont().

Solution:
Added clarification: "Make sure to set the font using textFont() before drawing text."

PR Checklist

• npm run lint passes
• Inline reference is included / updated
• Unit tests are included / updated

[welcome]

🎉 Thanks for opening this pull request! For guidance on contributing, check out our contributor guidelines and other resources for contributors!
🤔 Please ensure that your PR links to an issue, which has been approved for work by a maintainer; otherwise, there might already be someone working on it, or still ongoing discussion about implementation. You are welcome to join the discussion in an Issue if you're not sure!
🌸 Once your PR is merged, be sure to add yourself to the list of contributors on the readme page !

Thank You!

[ksen0]

If the test runs, then this sounds reasonable and helpful! I checked the failing test and I'm not sure what was up, I reran. If it fails, then code would need to be updated so tests do pass.

Minor wording revision to keep the message same length:

WEBGL: requires Opentype (.otf) or Truetype (.ttf) font, loaded using textFont() before drawing text.

cc @davepagurek @perminder-17

[yugalkaushik]

@ksen0 all tests are passing now.

[davepagurek]

Thanks! Would you be interested in making a similar update to the dev-2.0 branch, which p5 2.x builds are made from?