Update digitization.md
Update digitization.md

Adding photo links to walkthrough.
cheelee/ChannelWorm,gsarma/ChannelWorm,joebowen/ChannelWorm,cheelee/ChannelWorm,openworm/ChannelWorm,joebowen/ChannelWormDjango,gsarma/ChannelWorm,joebowen/ChannelWormDjango,joebowen/ChannelWormDjango,gsarma/ChannelWorm,joebowen/ChannelWormDjango,VahidGh/ChannelWorm,joebowen/ChannelWorm,VahidGh/ChannelWorm,cheelee/ChannelWorm,cheelee/ChannelWorm,joebowen/ChannelWorm,openworm/ChannelWorm,VahidGh/ChannelWorm,openworm/ChannelWorm,gsarma/ChannelWorm,joebowen/ChannelWorm,VahidGh/ChannelWorm,openworm/ChannelWorm