fix: clone propsData to avoid mutation

[briwa]

Potentially fix #393.

In the issue it was mentioned that cloning might cause other problems with stubbing. Was wondering if doing this might break it? Seems like all other tests are passing, maybe I'm missing something 🤔 @eddyerburgh

Also, I've added a test to make sure it won't happen again, but I am not sure if this is the best way to do it, whether it belongs to mounting-options or not, whether the test structure adheres the repo standard, etc. I'm open for suggestions.

Thanks.

[eddyerburgh]

Cloning will be fine with stubs. I thought cloning a function would break the reference, but I was wrong.

You need to fix a flow error. You can add a propsData property to the options object in flow/options.flow.js.

Then I'm happy to merge 👍

[briwa]

Alright, fixed @eddyerburgh. Thanks.

[eddyerburgh]

Thanks for the quick fix