title: p5.Vector not respecting angleMode
body: <p>I've noticed that when rotating vectors, the rotation is done in radians even after I have called <code>angleMode</code> with <code>DEGREES</code>. This behaviour only appears with vectors declared using the <code>new p5.Vector</code> syntax, while using <code>createVector</code> avoids it.</p>
  <p>Minimal reproducible example: (paste into p5 web editor or OpenProcessing)</p>
  <pre class="lang-js prettyprint-override"><code>function setup() {
      createCanvas(400, 400)
      translate(100, 100) // To see the effect more clearly
      angleMode(DEGREES)
      let v = new p5.Vector(1, 0)
      line(0, 0, v.x * 50, v.y * 50)
      v.rotate(HALF_PI)
      line(0, 0, v.x * 50, v.y * 50)
  }
  </code></pre>
  <p>Notice that the rotation is still done in radians. If you replace <code>new p5.Vector</code> with <code>createVector</code> then the problem disappears. Why is this?</p>