Sorts tabs by URL. Access via accel-shift-o or the button.
a-z icons from https://www.iconfinder.com/icons/905641/ascending_az_filters_sort_sorting_icon
which is under https://creativecommons.org/licenses/by/3.0/
Changes:
0.5: ported to webextensions button instead of tools menu
0.3: added tools menu item. added source to github.