<div>
   <span class='title'>TITLE GOES HERE</span>
   <canvas id="bar" width="390" height="225"></canvas>
</div>


CSS :
canvas {
  display:inline;
}
.title {
    font-size: 47px;
    font-weight: bold;
    opacity: 0.2;
    z-index: -1;
    margin-top: 20px;
    position: absolute;
}

let myLineExtend = Chart.controllers.line.prototype.draw;
Chart.helpers.extend(Chart.controllers.line.prototype, {
  draw: function() {
    myLineExtend.apply(this, arguments);
    // text styles below
    this.chart.chart.ctx.textAlign = "center"
    this.chart.chart.ctx.font = "20px Arial black";
    this.chart.chart.ctx.fillText("Lorem Ipsum Blah Blah", 300, 150)  // text, x-pos, y-pos
  }
});