PyItemTemplate.strike() uses the CSS class line-through, which was part of Tailwind. Reintroduce it in our custom CSS. This fixes the todo-pylist example (#638)

pyscriptjs/src/styles/pyscript_base.css

@@ -238,3 +238,7 @@ button, input, optgroup, select, textarea {
     line-height: 1.15;
     margin: 0;
 }
+
+.line-through {
+    text-decoration: line-through;
+}