Added documentation comments for LoadDirectoryFilesEx

[XenoMustache]

Added the lines

// Use 'DIR*' to include directories on directory scan
// Use '*.*' to include all file types and directories on directory scan

To reflect new FILE_FILTER_TAG_ALL and FILE_FILTER_TAG_DIR_ONLY macros. These resolved to *.* and DIR* respectively.

[raysan5]

@XenoMustache thanks for the improvement, note that you can also use the macro names, they are there for convenience, and they can also be customized if desired