Authors: Add four missing authors, mostly selectmenu contributors

These authors were probably missed during earlier updates due to their commits to the selectmenu branch, were `grunt authors` showed their names above newer authors that contributed directly to master.

I would usually push authors updates directly to master. Though in this case I'd like to point out the limitation of `grunt authors`. Can we avoid this problem in the future?

Btw. I found the missing names by sorting both `AUTHORS.txt` and the output of `grunt authors` alphabetically, then diffing them. Ignore removed lines, pay attention to added lines.