Add dismissible mechanism for WCAG 2.1 SC 1.4.13

Problem/Motivation

Currently, the tooltip does not comply with the WCAG 2.1 Success Criterion 1.4.13 (Content on Hover or Focus) because it cannot be dismissed.

Dismissible
A mechanism is available to dismiss the additional content without moving pointer hover or keyboard focus, unless the additional content communicates an input error or does not obscure or replace other content;

Proposed resolution

Implement a feature that allows the tooltip to be dismissed using the Escape key.