Missing function to create png/jpeg images

[linev]

Up to now only makeSVG function was provided.

It is not possible to create images for different objects types.

[linev]

Now makeImage function will be introduced. It supports 'png', 'svg' and 'jpeg' image formats.

Usage examples are shown in make_image.htm and make_image.js demos.

Link on dev version: https://jsroot.gsi.de/dev/api.htm#custom_html_create_image

[linev]

Unfortunately, there is one unresolved issue with node-canvas component, used for image production in node.js.

It is reported now here: Automattic/node-canvas#2254

Because of this limitation embed images like lego plots on the canvas are not working in node.js.
I hope solution will be find.
Issue does not affect SVG image generation - produced by JSROOT svg images can be used without limitation and, if necessary, converted to any other formats.

[linev]

Function appears in https://github.com/root-project/jsroot/releases/tag/7.4.0

Keep open until issue with node-canvas is not resolved.