build(spa): Add index.html for experimental SPA (#17586)
build(spa): Add index.html for experimental SPA (#17586)

The logic here is slightly incorrect, we want to add the index.html when
SENTRY_EXPERIMENTAL_SPA is enabled, which will be true whe
DEPLOY_PREVIEW_CONFIG is configured.
beeftornado/sentry,beeftornado/sentry,beeftornado/sentry