[project page] Fix broken link

index.html

@@ -129,7 +129,7 @@
     <li><a href="demo/variableheight.html">Mixing font sizes and styles</a>
     <li><a href="demo/theme.html">Various themes</a>
     <li>Able to <a href="demo/resize.html">resize to fit content</a>
-    <li><a href="doc/manual.html#mark_replacedWith">Inline</a> and <a href="doc/manual.html#setLineWidget">block</a> widgets
+    <li><a href="doc/manual.html#mark_replacedWith">Inline</a> and <a href="doc/manual.html#addLineWidget">block</a> widgets
     <li>Programmable <a href="demo/marker.html">gutters</a>
     <li>Making ranges of text <a href="doc/manual.html#markText">styled, read-only, or atomic</a>
     <li><a href="demo/bidi.html">Bi-directional text</a> support