Fix typo in 01-The-Basics.md

Another alternative might be: `... both encodings using ...`

Author: smfoote

manuscript/01-The-Basics.md

@@ -4,7 +4,7 @@ ECMAScript 6 makes a large number of changes on top of ECMAScript 5. Some of the
 
 ## Better Unicode Support
 
-Prior to ECMAScript 6, JavaScript strings were based solely on the idea of 16-bit character encodings. All string properties and methods, such as `length` and `charAt()`, were based around the idea that every 16-bit sequence represented a single character. ECMAScript 5 allowed JavaScript engines to decide which of two encodings to use, either UCS-2 or UTF-16 (both encoding using 16-bit *code units*, making all observable operations the same). While it's true that all of the world's characters used to fit into 16 bits at one point in time, that is no longer the case.
+Prior to ECMAScript 6, JavaScript strings were based solely on the idea of 16-bit character encodings. All string properties and methods, such as `length` and `charAt()`, were based around the idea that every 16-bit sequence represented a single character. ECMAScript 5 allowed JavaScript engines to decide which of two encodings to use, either UCS-2 or UTF-16 (both encodings use 16-bit *code units*, making all observable operations the same). While it's true that all of the world's characters used to fit into 16 bits at one point in time, that is no longer the case.
 
 Keeping within 16 bits wasn't possible for Unicode's stated goal of providing a globally unique identifier to every character in the world. These globally unique identifiers, called *code points*, are simply numbers starting at 0 (you might think of these as character codes, but there is subtle difference). A character encoding is responsible for encoding a code point into code units that are internally consistent. While UCS-2 had a one-to-one mapping of code point to code unit, UTF-16 is more variable.