Bruce Mitchener: Minor typo fixes.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@175274 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/www/atomic_design.html b/www/atomic_design.html
index 87a2f62..2314841 100644
--- a/www/atomic_design.html
+++ b/www/atomic_design.html
@@ -37,7 +37,7 @@
 
 <p>
 There are currently 3 designs under consideration.  They differ in where most
-of the implmentation work is done.  The functionality exposed to the customer
+of the implementation work is done.  The functionality exposed to the customer
 should be identical (and conforming) for all three designs.
 </p>