universal binary support

New features:

• universal binary (but not yet tested on Apple Silicon M1).
• add support for edu.uo.texshop.tex UTI used by .tex files.
• highlight updated to version 3.59 compiled as universal binary with lua 5.4.1 statically linked.
• The embedded lua library used by the main application is upgraded to version 5.4.1.

Bugfix:

• fixed a bug for the missing preview in html mode on the settings window.
• predefined output mode set to .rtf (less expansive that html).