bug: Ion Skeleton Text Animation is hard to see through to work in dark mode

### Describe the Bug

You can barely see ion-skeleton-text on a black/dark background when animated. I can not customize the colors any further when animated.

### Expected Behavior

ion-skeleton-text is either customizable to become visible or is already visible.

### Steps to Reproduce

ion-skeleton-text {
--background: rgba(240, 238, 228, 1);
--background-rgb: 240, 238, 228;
}
put ion-skeleton-text with animated true over black or dark background.

### Screenshots


### Operating System

Windows

### Browser

Chrome

### Version

_No response_

### Additional Information

Ionic v8, React app.

Begin with the ion-skeleton-text component and reproduce the animated case on a dark background using the supplied CSS custom properties. Trace the animation styling and verify the result against the expected behavior: the skeleton should be visibly customizable or already visible in dark mode.

Written by the indexing model from the issue text.