Improve visibility of mouse director indicator

[Stehsaer]

Default indicator is colored red, but in actual play the indicator's visibility is not so good. Some improvements are requested. Potential improvements may be:

1. add a white outline to the indicator
2. use a black bar with white outline or white bar with black outline as the indicator
3. make it configurable, can be set through dragging images into mod folder and editing the .cfg files

[Stehsaer]

what's more, instead of bar, using a cross may be even better. for this reason I strongly recommend adding a customizable indicator image setting.

[Stehsaer]

https://github.com/Boris-Barboris/AtmosphereAutopilot/blob/9e4323c9ebd91d4250662bec152c23ce8250cca7/AtmosphereAutopilot/Modules/MouseDirector.cs#L119-L145 It's here that should be modified.