Expose SSE events parser (`internal/parser`)

[tmaxmax]

Hey, I was searching around for only an SSE events parser - encoder/decoder. This was the only library I could find that isn't ancient - thanks for your work!

I'm using an openapi spec which generates ready to use API calls from client side - which is why I am not using the client in go-sse (it would take time to make it play well with openAPI generated code). However, I'm interested in using the code inside internal/parser. I could also help you with exposing it if you had a few ideas in mind.

I saw that the code in https://github.com/donovanhide/eventsource/blob/master/decoder.go, was much simpler and shorter than what you have written up - is there any advantage that I'm missing to your implementation? Please do let me know!

Thanks!

Originally posted by @Pramodh-G in https://github.com/tmaxmax/go-sse/issues/7#issuecomment-2209454186