Provide development apps that contains irregular cache data

We recently found out that removing the `JSON.stringify` in https://github.com/apollographql/apollo-client-devtools/pull/1245 caused some [issues](https://github.com/apollographql/apollo-client-devtools/issues/1258) related to transporting the cache to the devtools. Unfortunately we could not catch this in development/testing because we don't have a sample application that provides some of the irregularities we see in real world apps. This is also very difficult to test in an automated way because there is virtually no way to run an automated end-to-end test for a browser extension.

Our next best option would be to create a development app that we can fill with some of these edge cases so that we can test these ourselves before we release.

Review pull request #1245 and issue #1258 first, then inspect the repository's existing development-app setup. Add a development app containing the irregular cache cases described by the maintainers, and verify that the cache can be transported to the devtools for manual pre-release testing.

Written by the indexing model from the issue text.