Added "Transparent with light text" theme for Desktop Notes

Summary:
This commit adds one more simple theme for Desktop Notes, for ones who prefer the dark background and want to put sticky notes on it.

BUG: 386833

Before:

After:

Reviewers: Plasma, davidedmundson

Reviewed By: Plasma, davidedmundson

Subscribers: shubham, abetts, ngraham, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D17360