[css-values-5] More sensible heading structure

Author: fantasai

css-values-5/Overview.bs

@@ -42,6 +42,11 @@ Module Interactions</h3>
 	<a href="https://www.w3.org/TR/CSS21/syndata.html#values">4.3</a>,
 	and <a href="https://www.w3.org/TR/CSS21/aural.html#aural-intro">A.2</a>.
 
+<h2 id="textual-values">
+Textual Data Types</h2>
+
+	See [[css-values-4#textual-values]].
+
 <!--
 ██     ██ ████████  ██
 ██     ██ ██     ██ ██
@@ -105,6 +110,8 @@ Request URL Modifiers</h4>
 		given |req|.
 	</div>
 
+<h2 id="value-insert">
+Miscellaneous Value Substituting Functions</h2>
 
 <!--
 ████████  ███████   ██████    ██████   ██       ████████   ███ ███
@@ -249,8 +256,8 @@ Toggling Between Values: ''toggle()''</h3>
 ██     ██    ██       ██    ██     ██   ███ ███
 -->
 
-<h2 id="attr-notation">
-Attribute References: the ''attr()'' function</h2>
+<h3 id="attr-notation">
+Attribute References: the ''attr()'' function</h3>
 
 <!--
 Ian's proposal:
@@ -329,8 +336,8 @@ Ian's proposal:
 		like in ''width: attr(size px, auto);''.
 	</div>
 
-<h3 id="attr-types">
-''attr()'' Types</h3>
+<h4 id="attr-types">
+''attr()'' Types</h4>
 
 	The behavior of the ''attr()'' function
 	depends partially on the value of the <<attr-type>> argument:
@@ -457,8 +464,8 @@ Ian's proposal:
 		</pre>
 	</div>
 
-<h3 id=attr-substitution>
-''attr()'' Substitution</h3>
+<h4 id=attr-substitution>
+''attr()'' Substitution</h4>
 
 	Issue: attr() and var() substitute at the same time,
 	so I should probably rewrite [=substitute a var()=]