🔧(react) rollup type files

Previously types file were splitted into their original folder
tree structure. By enabling this option we could just get one
global .d.ts file. To make this more handy I created a dedicated
build bash file, the package.json was starting to get messy.

.changeset/khaki-bananas-leave.md

@@ -0,0 +1,5 @@
+---
+"@openfun/cunningham-react": minor
+---
+
+fix type files imports and rollup them