add example to get width of a string

[mustmodify]

Took me almost an hour to weave my way through this logic... thought I could save someone the time.

[practicingruby]

Thanks, this looks helpful! There are some Rubocop failures, which I can clean up when I get around to merging this, but if you'd like to sort those out you're welcome to.

[pointlessone]

@mustmodify Thank you for your contribution.