docs: ADR to make redux dependency optional

docs/decisions/0006-make-redux-deps-optional.rst

@@ -0,0 +1,60 @@
+Consumers of frontend-platform that don't use redux are still required to install redux dependencies
+==========================================
+
+Status
+------
+
+Review
+
+Context
+-------
+
+Some consumers of frontend-platform, such as frontend-app-learner-portal-enterprise, no longer use redux or react-redux.
+However, they are still required to install these dependencies due to the usage of react-redux in AppProvider, and the fact that
+react-redux and redux are peerDependencies. To be precise, the OptionalReduxProvider used by AppProvider is what uses the
+react-redux Provider in case a store prop is passed to AppProvider.
+
+Specifically, if an app like frontend-app-learner-portal-enterprise were to uninstall the redux and
+react-redux dependencies, it fails with an error during module loading like this::
+
+    ERROR in ./node_modules/@edx/frontend-platform/react/OptionalReduxProvider.js 3:0-39
+    Module not found: Error: Can't resolve 'react-redux' in 'frontend-app-learner-portal-enterprise/node_modules/@edx/frontend-platform/react'
+
+Therefore, redux and react-redux are only optional from a code perspecitve, not from a dependency perspective right now.
+This means there is extra overhead and confusion on seeing 'redux' and 'react-redux' in such projects, when they are not leveraging the `store` feature of AppProvider.
+
+It will be great to be able to not have to include redux and react-redux as dependencies in such cases.
+
+Decision
+--------
+
+A method to enable the removal of the dependencies `redux` and `react-redux` from mentioned client projects is to leverage optionalDependencies.
+
+According to `npm documentation <https://docs.npmjs.com/cli/v8/configuring-npm/package-json#optionaldependencies>`_:
+
+> optionalDependencies are dependencies that do not necessarily need to be installed.
+  If a dependency can be used, but you would like npm to proceed if it cannot be found or fails to install,
+  then you may put it in the optionalDependencies object.
+
+Therefore if we were to move the redux and react-redux into optionalDependencies instead, consumers will no longer fail build
+when these deps are missing.
+
+In addition, since the `OptionalReduxProvider` makes use of the import of react-redux, it may need to also make a safe import such that
+a missing package react-redux does not cause a failure, as noted in the above link. Instead it can simply detect the absence of the package
+and return, something like this::
+
+    if (store === null || !Provider) {
+        return (
+        <>{children}</>
+        );
+    }
+
+
+Consequences
+--------
+
+For consumers that use frontend-platform but do make use of the redux store feature of AppProvider, there should be no impact.
+
+However, for consumers that do not use that feature, they should no longer need to depend on redux or react-redux.
+
+Also, this will help bundle sizes to be smaller for consumers where this exclusion applies.