Fixes 65851408_about_strings_master

* I learned a lot about strings!
* I learned the differences between double and single-quoted strings (mainly interpolation and escaping for   
  both)
* I learned about flexible quoting
* I learned about concatenating strings (and they will leave the original strings unmodified)
* I learned about the differences between '+=' and << (shovels)
* Shovels do modify the original string and are favored because they don't create new objects (faster)
* I learned to get substrings and single characters from strings
* I learned how to split strings and to join them
* I learned that strings are unique objects even if their content is the same

[#65851408]