[Task]: Change node shape to circle

[begonaalvarezd]

Task description

Change node shape to circle

    const nodesFS = [
        "precision mediump float;",
        "varying vec4 color;",
        "void main(void) {",
        "   vec2 center = vec2(0.5);",
        "   float radius = 0.5;",
        "   if (length(gl_PointCoord - center) < radius) {",
        "     gl_FragColor = color;",
        "   } else {",
        "     gl_FragColor = vec4(0);",
        "   }",
        "}"
    ].join("\n");