Add .at( ) to strings summary

Author: joaquinelio

1-js/05-data-types/03-string/article.md

@@ -505,7 +505,7 @@ This method actually has two additional arguments specified in [the documentatio
 
 - There are 3 types of quotes. Backticks allow a string to span multiple lines and embed expressions `${…}`.
 - We can use special characters, such as a line break `\n`.
-- To get a character, use: `[]`.
+- To get a character, use: `[]` or `at` method.
 - To get a substring, use: `slice` or `substring`.
 - To lowercase/uppercase a string, use: `toLowerCase/toUpperCase`.
 - To look for a substring, use: `indexOf`, or `includes/startsWith/endsWith` for simple checks.
@@ -519,4 +519,4 @@ There are several other helpful methods in strings:
 
 Strings also have methods for doing search/replace with regular expressions. But that's big topic, so it's explained in a separate tutorial section <info:regular-expressions>.
 
-Also, as of now it's important to know that strings are based on Unicode encoding, and hence there're issues with comparisons. There's more about Unicode in the chapter <info:unicode>.
+Also, as of now it's important to know that strings are based on Unicode encoding, and hence there're issues with comparisons. There's more about Unicode in the chapter <info:unicode>.