[feature request] expand applet hitboxes to screen edges

[jmbuhr]

I feel like the current implementation makes it hard to click on or hover over an applet quickly, because each applet has a margin. So e.g. if one puts the mouse cursor at the screen edge over the workspace number applet, it is not on the applet, so scrolling doesn't trigger switching workspaces. Expanding the hitbox of an applet to the screen edges would make this a lot more seamless. Similarly, clicking e.g. the power applet would have less friction if it also triggered when the mouse is in the corner of the screen.

Related: #828