[css-fonts-4] Use correct terminology w/r/t "variable fonts" and "font variations"

#516

Author: Litherum

css-fonts-4/Overview.bs

@@ -29,7 +29,7 @@ controls CSS provides for selecting and using fonts within documents.
 The ideas here are additions or modifications to the properties and
 rules defined in CSS3 Fonts.</p>
 
-	Issue: Please note that OpenType/TrueType variation font support
+	Issue: Please note that OpenType/TrueType variable font support
 	is still in intial stages of specification and implementation. Please
 	comment on any bugs in this spec at <a href="https://github.com/w3c/csswg-drafts/issues">
 	https://github.com/w3c/csswg-drafts/issues</a>. Also, please note that this
@@ -1113,6 +1113,8 @@ at least as dark as its predecessor. Only values between 1 - 999 are valid, and
 
 <h2 id="font-variation-props">Font Variation Properties</h2>
 
+    Note: The technology in use in this section is named "font variations." An instance of one such font as a "variable font."
+
 <h3>Optical sizing control: the 'font-optical-sizing' property</h3>
 
 	<pre class="propdef">