Add draw-highlight action icons

Summary:
This patch adds draw-highlight icons requested by Okular for D15580.

I went with a style of showing the whole marker to be consistent with our other draw-* icons.
The stroke is 2px thick to illustrate the broad tip of the highlighter.

CCBUG: 408283

Test Plan: {F7547615}

Reviewers: #vdg, ngraham, ndavis

Reviewed By: #vdg, ngraham, ndavis

Subscribers: ngraham, ndavis, kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D24493