♻️(react) add a scroller div inside modal

Having the position fixed and at the same time overflow auto on the same
element was causing absolute children to be cropped. We need to set those
two attribute on two different parent for these children to not be cropped.
Yes this is weird, this is CSS.

.changeset/early-dryers-serve.md

@@ -0,0 +1,5 @@
+---
+"@openfun/cunningham-react": patch
+---
+
+♻️(react) add a scroller div inside modal