:demo: support emphasis mark

demo/2-declaritive-styles.ts

@@ -161,6 +161,10 @@ doc.addSection({
                     text: "and then underlined ",
                     underline: {},
                 }),
+                new TextRun({
+                    text: "and then emphasis-mark ",
+                    emphasisMark: {},
+                }),
                 new TextRun({
                     text: "and back to normal.",
                 }),