Multi-file demos
An external demo's entry file can import other local files, and the whole import graph comes along — one editor tab per file:
Loading demo…
Only the entry file is named in the MDX. Tabs are labelled by each file's path
relative to the entry's directory, so buttons/styles.ts and cards/styles.ts
stay distinct.
The import statements inside demo files resolve like your bundler's, and
can be extensionless: ./Button is tried as .tsx, .ts, .jsx, .js, then
Button/index.*.