en-US-x-pirate: pronunciation of some words for TTS

As I am working on voice prompts, I have some issues with the text-to-speech conversion of few en-US-x-pirate prompts. The software that I use (MycroftAI/mimic) for TTS supports SSML and can handle `phoneme` syntax. Now, would be great to have a list of pronunciation for few tricky words. Since I am not native speaker and not in linguistics either, its a bit tricky for me. Anyway, so far, I have issues with:

* Arrr
* Cap'n
* th'
* head'n

Maybe we can come out with some recommended phoneme sequences that all of us can use. I can extend the list of problematic words and assign phoneme sequences to them as the work on the issue progresses.