Fixed loading widget in new UI

[DistantVoyager]

Closes: #3742

What's Changed

• Centered the LoadingWidget component in UI.
• Lightened the color of the LoadingWidget text to gray-3.
• Also updated the endColor of the skeleton loading animation (when tables load) to a lighter gray so it's easier on the eyes.

TODO

• Explanation of Change(s)
• Added change log fragment(s) (for more information see the documentation)

[glennmatthews]

Thanks for the pull request! I like the idea, but we may not be able to go in this direction as-is due to the need to support custom branding of an installed Nautobot instance.

[bryanculver]

Thanks for the idea @DistantVoyager!

[DistantVoyager]

@bryanculver @glennmatthews - Of course! This PR also correctly centers the LoadingWidget component and lightens the SkeletonText & loading widget text colors - do you guys want those changes? (if so I can create a new PR with just those minor fixes)

Currently:

Correctly Centered:

[bryanculver]

Sure! you can update and re-open.

[HanlinMiao]

Thanks for the PR! LGTM!