Add support for MDX (#17)

* feat: add support for MDX

* fix: prevent empty server handler error message

* doc: add MDX mention to README

* feat: update version to v0.7.0

examples/mdx/src/routes/__root.tsx

@@ -0,0 +1,14 @@
+import type { ReactNode } from 'react'
+import { MDXProvider } from '@mdx-js/react'
+
+interface RootRouteProps {
+  children: ReactNode
+}
+
+export default function RootRoute({ children }: RootRouteProps): JSX.Element {
+  return (
+    <main className="main">
+      <MDXProvider components={{}}>{children}</MDXProvider>
+    </main>
+  )
+}