Add resource links to 2021-12-01-mosaic-fusion.md

[GenevieveBuckley]

This PR adds several additional resource links to the "Also see" section of the mosaic image fusion blogpost.

I recently had a recent conversation with someone who read this blogpost and asked about other tools. That discussion resulted in links to several software packages I was unfamiliar with. I think it would be a good idea to include them in the further reading section, for any future readers also interested in this area.

[pavithraes]

@GenevieveBuckley Thank you for adding these links, it looks good to me!

Would you mind updating the bullet point to be defined with - instead of * to make the linter happy? We can merge after. :)

[GenevieveBuckley]

Would you mind updating the bullet point to be defined with - instead of * to make the linter happy? We can merge after. :)

Of course, done!