fix missing punctuation in docs (#50126)

* fix missing punctuation

* Update types.md

---------

Co-authored-by: Viral B. Shah <ViralBShah@users.noreply.github.com>

Author: sciprosk

doc/src/manual/types.md

@@ -57,9 +57,9 @@ kinds of programming, however, become clearer, simpler, faster and more robust w
 The `::` operator can be used to attach type annotations to expressions and variables in programs.
 There are two primary reasons to do this:
 
-1. As an assertion to help confirm that your program works the way you expect,
+1. As an assertion to help confirm that your program works the way you expect, and
 2. To provide extra type information to the compiler, which can then improve performance in some
-   cases
+   cases.
 
 When appended to an expression computing a value, the `::` operator is read as "is an instance
 of". It can be used anywhere to assert that the value of the expression on the left is an instance