A visual difference between done and not-done tasks

I was thinking if we should do a 'strikethrough' effect on the tasks that are done, it is supported in a lot of terminals. Could use the ANSI escape sequence:

` \e[9m strikedthrough \e[0m`

If the terminal used doesn't have support, we could do a fallback that does the following, albeit pretty ugly:

`'T-e-s-t t-a-s-k t-e-x-t'`

I can do a PR that does this if there is any interest.