resolve svelte/shared.js

[Rich-Harris]

it's possible for a third party component to try and import the wrong version of Svelte.
Changing this line should fix it:

+const relative = require('relative-require');

// later...

-if (!('shared' in options)) options.shared = options.format === 'es' && 'svelte/shared.js';
+if (!('shared' in options)) options.shared = options.format === 'es' && relative.resolve('svelte/shared.js', process.cwd());