Add a highlight tool to the annotation

[ionleu]

Is your feature request related to a problem? Please describe.

It's hard to call attention to important areas in screenshots without drawing shapes or arrows, which can be a bit clunky.

Describe the solution you'd like

Add a highlight tool so I can easily highlight text or sections of the image with a semi-transparent color.

Describe alternatives you've considered

Using boxes with low opacity, but it doesn’t look as clean or intuitive.

Additional context

Would be nice to have a few preset colors and adjustable opacity, like in most PDF readers or screenshot tools.

[rahulrana701]

I can add this.

[ionleu]

@rahulrana701,
great!

Let's start with #230 and we can continue.