Sequence Diagram 4+

* Fixes a recently observed crash in syntax highlighting - thank-you Ganesh.
* Fixes a defect that meant syntax highlighting was working incorrectly.
* Fixes a defect that meant users were unable to export as PNG with a transparent background
* Fixes an issue that meant users with a scroll wheel mouse did not see the participant HUD when scrolling - thank-you Andrew.
* Updates Copyright year to 2023.
* Updates Acknowledgments to reflect that no end user data is captured.
* Updated to improve rendering performance.
* Updates application icon imagery.
* Fixes a defect where the Acknowledgments window would not respect Dark mode.
* Fixes a defect where a note could be rendered outside the interaction frame it was declared in.
* Fixes a defect where the diagram text editor line numbers would not update, when the window was resized.
* Fixes a defect where the application could crash when exiting full screen mode.

Other recent enhancements :-
* Will now use the diagram “title” as the initial filename, if present.
* Adds support for Apple Silicon CPUs.
* Adds support for async signal arrow heads (see Help documentation, page 8).
* You can now tap interaction frame divider lines, to highlight the associated declaration in the diagram text.
* Adds support for Interaction Frame dividers using 3 dashes (---), which render a dashed line between signals in an Interaction Frame (see "New with Example [OPT+CMD+N]")
* Minor improvements to Participant HUD.
* Adds “Shows Participant HUD” menu option, to present the participants in an overlay, when the topmost participants are no longer entirely visible.
* Fixes a rare crash so ieen when the syntax highlights are applied.
* Fixes a defect where interaction frames containing only signals to self, would render incorrectly x2 so.Fixes a defect where reversed signals would always render with a solid signal line.

A massive thank-you for all the feedback, suggestions and bug reports (particularly from Andrew and Ganesh).

Please keep ‘em coming and don’t forget to rate and/or review.

Thanks again for your valued support.

-- Mike