* Update and rename strings.Rmd to strings.Rmd
Proposed fix related to this issue: https://github.com/hadley/r4ds/issues/807
A more comprehensive fix should perhaps discuss why "`{,m}`: at most m" does not work (or warn the reader that it does not)
* Typos in iteration.Rmd
Correcting two small typos
* Add missing word
* Add code example for 1,m
Co-authored-by: Mine Cetinkaya-Rundel <cetinkaya.mine@gmail.com>
