[css-inline] add illustration of initial letter with text indent

Author: dauwhe

css-inline-3/Overview.bs

@@ -1083,6 +1083,12 @@ Indentation and Multi-line Effects</h3>
 	apply to the first line of text as normal in the presence of initial letters.
 	Lines affected by the exclusion are shortened, as in the presence of floats,
 	and are affected the same way.
+	
+	<figure>
+		<img src="images/InitialLetterWithTextIndent.png" width="300"
+		     alt="initial letter with text indent">
+		<figcaption>Initial letter with text indent. </figcaption>
+	</figure>
 
 	If an initial letter is too long to fit on one line,
 	it wraps (according to the usual text-wrapping rules),