Improvements and bugfixes

To initiate a new Studio without installing the CLI globally:

npm create sanity@latest

To upgrade a v3 Studio, run this command in its folder:

npm install sanity@latest

• Various microcopy improvements
• Adds isSlug() method to @sanity/types for type-safe asserting of a slug object
• Fixes an issue where using multiple desk tools in the same studio would cause duplicate "review changes" actions and validation lists to appear. Thanks @andparsons!
• userHasRole will now accept null as well as a user object, making it more convenient in certain situations where the user might not yet be accessible
• Fixes issue with auto scrolling on collapsed fieldset
• Fixes issue where array list would not display all items when wrapped in a custom element
• Fixes issue where array list would not display when inside a popover