Tests adding a list through the UI, the add <thing> blocks, the reported value and adding items using the monitor UI

* Export initial states for each reducer
* combine all gui reducers (excludes scratchPaint and intl)
* combine all initial states to create default guiState for preloading in www
* expect all of the gui state to be accessible at `state.scratchGui`

- better split of hash-parser/project-loader unit tests.

The project loader that is exported with GUI just expects to be passed projectId as a prop, and it manages loading project data.

The part of the project loader that watches for URL hash changes for the playground is a new HOC that is only used in the various playground examples.

Question, should ‘x’ and ‘y’ be localizable?

This reverts commit 29d5619d.

* Updates to preview modal for release

* Design tweaks and remove import modal

* Resolve issues with tests

* Copy edits HT Eric

* Resolve lint issue with integration test

* One more change to the disclaimer language

* Add line break

They're spammy — happy to put this back but they were unhelpful while fixing tests IMO.

- export image and sounds in dist/static/assets
- rename main export (`scratch-gui.js`, not `index.js`)
- move project-loader-hoc back to lib (VM doesn’t load properly without it)

Allow intl to be passed in to GUI as a prop (rather than having to be already in the store)

Pages no longer reload if you hit the same hash URL twice

Resolves https://github.com/LLK/scratch-gui/issues/1713

Add a jest unit test for making sure the number is rendered out when
provided and not when not provided.