Update homepage, add demos data.

* display ydemo sections dynamically.
* Introduced a new `demos.ts` file for demo content management.
* Added `framer-motion` for animations and updated dependencies in `package.json`.

.run/main-website.run.xml

@@ -0,0 +1,12 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="main-website" type="js.build_tools.npm">
+    <package-json value="$PROJECT_DIR$/main-website/package.json" />
+    <command value="run" />
+    <scripts>
+      <script value="dev" />
+    </scripts>
+    <node-interpreter value="project" />
+    <envs />
+    <method v="2" />
+  </configuration>
+</component>