Improve syntax highlighting suggestions in readme (#164)

- Recognize Justfile as a justfile for vim filetypes snippet
- Add vim modeline and emacs local variables block

README.md

@@ -431,10 +431,19 @@ if exists("did_load_filetypes")
 endif
 
 augroup filetypedetect
-  au BufNewFile,BufRead justfile setf make
+  au BufNewFile,BufRead Justfile,justfile setf make
 augroup END
 ```
 
+Include the following in a `justfile` to enable syntax highlighting in vim and emacs:
+
+```
+# Local Variables:
+# mode: makefile
+# End:
+# vim: set ft=make :
+```
+
 Feel free to send me the commands necessary to get syntax hilighting working in your editor of choice so that I may include them here.
 
 ### justfile grammar