[FFmpeg-devel] request: add link to wiki on the docu page.

[Roger Pack]

Might be nice to add a link to
http://ffmpeg.org/trac/ffmpeg/wiki
within the documentation page:
http://ffmpeg.org/documentation.html
Since the wiki has some guides like filtering, etc.

(I didn't see the file for documentation.html in git anywhere, so I
assume I just have to ask it here for changes to it?)

Thanks!
-roger-