Importing Javascript errors from log files

Sending an event is a single POST request. Considering that this functionality is the only part you would be able to reuse from existing SDKs, I think it would be easier for you to just use curl: How can I post with curl a sentry event? Which authentication credentials?

Take a look at https://docs.sentry.io/development/sdk-dev/attributes/ to know which keys exist in the JSON payload.