Incorporating Michael's and Patrick's suggestions

Per @michael-n-cooper suggestions in the survey:

1. Wrapped "significant animation" in  so Respec will then pick up
the link to the definition.
2. Changed "whilst" to "while" for W3C's US English policy.
https://www.w3.org/2002/09/wbs/35422/SC_20170207/results#xq4

Per @patrickhlauke suggestions:

1. Changed "animation" to "animations”.
#96 (comment)
2. Added "(e.g. parallax scrolling effects)" after "synchronized with a
user action" to help clarify what is meant.
#96 (comment)

guidelines/index.html

@@ -600,8 +600,8 @@ Re-authenticating
       
 					Animation from interactions
 					A
-					Unchanged
-					For significant animation triggered by a user action that is not an essential part of the action, there is a mechanism for the user to pause, stop or hide the animation whilst still performing the same action.
+					New
+					For significant animations triggered by a user action that is not an essential part of the action, there is a mechanism for the user to pause, stop or hide the animations while still performing the same action.
 				
 			
 
@@ -1441,9 +1441,9 @@ Glossary
 					translation of one language, generally a spoken language, into a sign language
 					True sign languages are independent languages that are unrelated to the spoken language(s) of the same country or region.
 				
-        Significant animation
+        Significant animation
 				
-					animation which continues for more than 3 seconds, or is synchronized with a user action, and affects more than 1/3 of the viewport.
+					animation which continues for more than 3 seconds, or is synchronized with a user action (e.g. parallax scrolling effects), and affects more than 1/3 of the viewport.
 				
 				specific sensory experience