add rehype interface

packages/app/src/interfaces/rehype.ts

@@ -0,0 +1,6 @@
+export const RehypeSanitizeOption = {
+  Recommended: 1,
+  Custom: 2,
+} as const;
+
+export type RehypeSanitizeOption = typeof RehypeSanitizeOption[keyof typeof RehypeSanitizeOption];