gl2d: add user-select-none class to canvas
gl2d: add user-select-none class to canvas

- this sanitizes double clicks interactions
- e.g. double-click on the canvas now no longer puts
  the select-box in a weird state
- see https://github.com/plotly/plotly.js/issues/744 for more info

aburato/plotly.js,plotly/plotly.js,iongroup/plotly.js,plotly/plotly.js,asolagmbh/plotly.js,etpinard/plotly.js,plotly/plotly.js,iongroup/plotly.js,iongroup/plotly.js,etpinard/plotly.js,etpinard/plotly.js,aburato/plotly.js,asolagmbh/plotly.js,asolagmbh/plotly.js,plotly/plotly.js