✨(react) add tokens.ts files handling

These files will be used to define the custom design tokens per components.
They are automatically aggregated by the packages/react/cunningham.ts file,
this is why handling typescript config file was important.

packages/react/src/components/Button/tokens.ts

@@ -0,0 +1,8 @@
+import { DefaultTokens } from "@openfun/cunningham-tokens";
+
+export const tokens = (defaults: DefaultTokens) => {
+  return {
+    "border-radius": "5px",
+    shadow: "0px 0px 10px 1px " + defaults.theme.colors.primary + ";",
+  };
+};