Adds a sidebar widget to change text size in your WP site. Future feature: change colour contrast.
Follow the Installation instructions. Below are options you can set in the widget:-
Resize the following HTML/CSS tags: Specify all the HTML or CSS tags you want to resize in this section. By default, the HTML tag body, p, li and td is set. Different WordPress theme may have different and unique stylesheet classes and IDs. You can switch on your browser's built-in Developer Tools and use the Inspect Element option to detect what HTML/CSS codes to use.
Set to these sizes: This is where you set the font-size you want to enable for the users to use (read up on the CSS font-size property at W3Schools). The simplest font-size group you can use are smaller, inherit, larger.
Set controller text: By default, the widget displays the letter "T" depending on the number of font sizes you use; that is, if you set only two font-size, then only two letter T appears, and so forth. Starting with version 1.2, you can set it to use more meaningful words, like Small, Normal, Large for each size you specify.
Not tested, but theoretically yes, you can. Follow the Manual installation steps in the Installation section for details.