Hervé Girod - 2025-03-04

Ensure that the getSyntaxForExtension(File) and getSyntaxForExtension(String) methods always return a syntax (which may be the default syntax)
Support getting a Syntax from a MIME type
Add methods in the SyntaxMapper class to get a Syntax from a MIME type or an extension
Add methods in the JEditor class to set the Editor syntax from a MIME type or an extension