Make sure one notices one can now use GitHub to report bugs

[jidanni]

On https://sourceforge.net/projects/viking/ and then in https://sourceforge.net/p/viking/bugs/ there is no mention that one can now use https://github.com/viking-gps/viking/issues/ to report bugs.

[rnorris]

I don't have any direct control of the SourceForge bugs page to enable mentioning of this location.

Note there is a link to Github in the SourceForge 'tab' list of |Summary|Files|Reviews|etc... but it is the last item so may be hidden behind a hamburger menu or other '...' click to reveal more entries type thing.

However I have now extended the Summary description to make it more prominent that there is a Github presence as well. I hope that suffices.