Thanks https://github.com/zeke/semantic-pull-requests and now to
https://github.com/amannn/action-semantic-pull-request too.

* Draw the border—but don't scroll the page—when focusing on, or
hovering over, a landmark button in the GUI.
* Don't allow the border addition/removal to flash excessively.
* Add documentation for the next release.

…on (#480)

* Add an option to close the pop-up at the point of activating a
landmark's button.
* Ensure "pop-up" is used consistently in the codebase.
* Open the browser console when starting Firefox via web-ext.

Closes #477

This removes calls to Object.freeze() and Object.assign() from the built
code. The code could not be tree-shook (?) and needed to be flagged as
free of side effects.

If the user enters an empty string, the default value is used instead.

Fixes #484

Don't hide the border of the current element when highlighting or
un-highlighting via the pop-up when borders are persistent.

Note: if the user has the mouse hovered over a button when the pop-up is
closed by pressing the Escape key, that one will remain highlighted. The
blur event fires on the button if focused, but apparently the mouseleave
event doesn't. It also doesn't seem possible to detect the pop-up window
closing.

Oops!