Action definitions now support a couple additional settings:

ariaLabel can be can be provided to set a better label used for

  screen readers.
url can be set to use an <a href="..."> instead of a <button>.

Action button callbacks can also now return a Promise. This will cause

the button's contents to be replaced with a spinner and the button to be

disabled until the promise is resolved, making it clear when an action

is occurring and avoiding issues with the action being triggered

multiple times.
ListItem models also now have a convenient setActions() method for

setting new actions on the model and triggering the appropriate signal

to re-render the actions list.
To support the new capabilities, particularly the link buttons, the

styling had to be tweaked to increase rule specificity. This is because

for link actions, we set a btn class, and this is overridden in other

stylesheets in a way that caused our settings to be lost. The new rules

ensure we have higher specificity in any common case.

Tested our config forms usage with the new settings and saw that they

were all rendering correctly.
Tested the new Promise support, verifying the spinner replaced the

contents at the start of the operation and restored the contents at

the end.