fix: add splineVertex to p5.Graphics prototype and fix unit test error

[VANSH3104]

Resolves #7755

This pull request introduces a fix to the p5.Graphics prototype by adding the splineVertex method, which allows for more flexible spline drawing in the graphics context. Additionally, the corresponding unit test has been updated to reflect this change, addressing a previously encountered error in the test suite.

Changes:

• Added splineVertex method to p5.Graphics prototype.

• Fixed unit test error related to the splineVertex method.

• testing using this

suite('p5.Graphics.prototype.splineVertex', function() {
    test('should be a function in graphics', function() {
      let g = myp5.createGraphics(10, 10);
      assert.ok(g.splineVertex);
      assert.typeOf(g.splineVertex, 'function');
    });
  });

PR Checklist

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

[bojidar-bg]

I wonder if it might be possible to call customShapes similar to how primitives2D and the other addon functions are called in p5.Graphics.js - that might save a lot of repetition 😅

[VANSH3104]

@bojidar-bg Thanks a lot for the suggestion — that makes perfect sense!
I’ve added customShapes in Graphics.js and registered it just like you suggested.
Could you please take a look now and let me know if anything else needs tweaking?

[bojidar-bg]

Well.. you mention adding a unit test in the PR description and the commit message, but there's no unit test added in the changes themselves? (:'

[VANSH3104]

@bojidar-bg Ah, you're right — I mistakenly mentioned the unit test in the commit/PR but didn't include it in the actual changes 😅
I’ll add the unit test right away and push an update. Thanks for pointing that out!

[davepagurek]

Thanks for adding this!