upgrade structures and migrate to nextra v4

mdx-components.js

@@ -0,0 +1,11 @@
+import { useMDXComponents as getDocsMDXComponents } from 'nextra-theme-docs'
+
+const docsComponents = getDocsMDXComponents()
+ 
+// Merge components
+export const useMDXComponents = (components) => {
+  return {
+    ...docsComponents,
+    ...components
+  }
+}