Add system prompt

[Skeyelab]

add system prompt to the script gemeration. This could be tweaked from a drop down to get different styles of narration.

Here are some examples:

https://github.com/mustvlad/ChatGPT-System-Prompts/tree/main/prompts

[FujiwaraChoki]

System message should be added before user message, will merge once fixed!

[Skeyelab]

@FujiwaraChoki im not sure the order of the messages in the array matters, as they are sent to the API as a single object

[Skeyelab]

Let's forget this Pr. I've got something better coming