[css-grid-2] Add some IDs for linking.

Author: fantasai

css-grid-2/Overview.bs

@@ -139,35 +139,37 @@ Characteristics of a Subgrid Item</h3>
 	A <a>subgrid</a> behaves just like a normal <a>grid container</a> except that:
 
 	<ul style="list-style-type: lower-alpha">
-		<li>
+		<li id="subgrid-tracks">
 			The number of explicit tracks in each subgridded dimension
 			is given by its <a>grid span</a> in that dimension,
 			rather than by 'grid-template-rows'/'grid-template-columns'.
 			The track sizes are governed by the parent grid.
 
-		<li>
+		<li id="subgrid-indexing">
 			The <a>grid-placement properties</a> of the <a>subgrid</a>’s <a>grid items</a>
 			are scoped to the lines covered by the subgrid.
 			E.g., numeric indices count starting from the first line of the subgrid
 			rather than the first line of the parent grid.
 
-		<li>
+		<li id="subgrid-line-name-inheritance">
 			Since <a>subgrids</a> can be placed before their contents are placed,
 			the subgridded lines
 			automatically receive the line names
 			specified on the corresponding lines of the parent <a>grid</a>.
 			These names are in <em>addition</em> to
 			any line names specified locally on the subgrid.
 
-		<li>
+		<li id="subgrid-size-contribution">
 			The <a>subgrid</a> itself lays out as an ordinary <a>grid item</a> in its parent grid,
 			but acts as if it was completely empty for sizing purposes
 			in the subgridded dimension.
 
-		<li>The <a>subgrid</a>'s own <a>grid items</a> participate
+		<li id="subgrid-item-contribution">
+			The <a>subgrid</a>'s own <a>grid items</a> participate
 			in the sizing of its parent grid in the subgridded dimension(s)
 			and are aligned to it in those dimensions.
 
+			<p id="subgrid-margins">
 			In this process, the sum of the <a>subgrid</a>'s
 			margin, padding, and borders at each edge
 			are applied as an extra layer of (potentially negative) margin
@@ -203,6 +205,7 @@ Characteristics of a Subgrid Item</h3>
 				and the <a>grid item's</a> own position.
 			</div>
 
+			<p id="subgrid-gaps">
 			Meanwhile,
 			half the size of the difference between
 			the subgrid’s <a>gutters</a> ('row-gap'/'column-gap')
@@ -321,7 +324,7 @@ Characteristics of a Subgrid Item</h3>
 				</dl>
 			</div>
 
-		<li>
+		<li id="subgrid-implicit">
 			The <a>subgrid</a> does not have any <a>implicit grid tracks</a>
 			in the subgridded dimension(s);
 			every <a>grid area</a> within it is <a>clamped</a> to its <a>explicit grid</a>.
@@ -331,18 +334,18 @@ Characteristics of a Subgrid Item</h3>
 				then that item is instead forced into (and limited to) the first (only) track in the subgrid.
 			</div>
 
-		<li>
+		<li id="subgrid-box-alignment">
 			The <a>subgrid</a> is always stretched in its subgridded dimension(s:
 			the 'align-self'/'justify-self' properties on it are ignored,
 			as are any specified width/height constraints.
 
-		<li>
+		<li id="subgrid-grid-alignment">
 			Layoutwise, the <a>subgrid</a>’s <a>grid</a>
 			is always aligned with the corresponding section of the parent <a>grid</a>;
 			the 'align-content'/'justify-content' properties on it are also ignored
 			in the subgridded dimension.
 
-		<li>
+		<li id="subgrid-overflow">
 			The 'overflow' property does apply to <a>subgrids</a>,
 			so that overflowing contents of the subgrid can be scrolled into view.
 			(Note: the act of scrolling does not affect layout.)