Improvements to error state: input outline shows with or without focus, and added new error div which shows if there's an error, but goes away if the user starts changing what they had submitted in the input. Removing a lot of code surrounding the tooltip which has now become unnecessary.

Import input now shows error state w/orange border around input and tooltip with static error message.

Initial SB2 Import UI (button in preview modal + import modal that can load projects via url). Preliminary validation on url, still needs error handling.

- Call scrollToCategoryByName('My Blocks') after custom block is created
- Cannot assume custom blocks section will be last category
- May pose issue during localization efforts

Use the same drag threshold as from the blocks. It may need to be dialed
in further, but testing will be needed.

Images are draggable by default, but when used within buttons or as
clickable elements, they should not be draggable because starting a drag
accidentally prevents the click event.

Since we will be adding more interactivity, the active state will
eventually pop the menu open, so I'm not worried about accessibility of
this right now.

It claims to support other sample rates, as the spec requires, but it
does not.

This is a long standing issue with how iOS deals with scrollable
elements within a fixed area. This was a helpful resource
https://davidwalsh.name/scroll-iframes-ios

Showing/hiding 'more options' in the different types of variable prompts based on var type provided from scratch blocks