patch 9.0.0182: quarto files are not recognized

Problem:    Quarto files are not recognized.
Solution:   Recognize quarto files by the extension. (Jonas Strittmatter,
            closes #10880)

runtime/filetype.vim

@@ -1531,6 +1531,9 @@ au BufNewFile,BufRead *.ptl,*.pyi,SConstruct		   setf python
 " QL
 au BufRead,BufNewFile *.ql,*.qll		setf ql
 
+" Quarto
+au BufRead,BufNewFile *.qmd     setf quarto
+
 " Radiance
 au BufNewFile,BufRead *.rad,*.mat		setf radiance