Set up some smoke tests for packaging

[KittyGiraudel]

@drwpow-figma I started with the approach you recommended in #702. It works perfectly fine for the CJS tests, but the ESM ones fail like this:

node:internal/process/esm_loader:34
      internalBinding('errors').triggerUncaughtException(
                                ^

Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'a11y-dialog' imported from /Users/kitty/Sites/a11y-dialog/cypress/fixtures/esm/test.js
Did you mean to import a11y-dialog/cypress/fixtures/dist/a11y-dialog.esm.js?
    at packageResolve (node:internal/modules/esm/resolve:853:9)
    at moduleResolve (node:internal/modules/esm/resolve:910:20)
    at defaultResolve (node:internal/modules/esm/resolve:1130:11)
    at ModuleLoader.defaultResolve (node:internal/modules/esm/loader:396:12)
    at ModuleLoader.resolve (node:internal/modules/esm/loader:365:25)
    at ModuleLoader.getModuleJob (node:internal/modules/esm/loader:240:38)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:85:39)
    at link (node:internal/modules/esm/module_job:84:36) {
  code: 'ERR_MODULE_NOT_FOUND'
}

Do you have an idea why?

[drwpow-figma]

Yes see comment above—we want to make sure we’re using the dist/ in the root, and not copying it anywhere else.

Or, if Cypress needs a special setup to make it happy, that’s fine. But the vanilla Node.js tests should be using the root dist folder, that way you’re sure you’re testing the package exactly as it ships to npm.