Use &str or String instead of &'static str in RenderConfig

[arturfast]

Is your feature request related to a problem? Please describe.
I'd like to customize my prompt prefix in the Text menu using the format! macro. This is not possible due to prompt_prefix being defined as a &'static str in RenderConfig. This is limiting because I can only pass string literals instead of formatted Strings or &str.

Describe the solution you'd like
I'd like to change the parameters of all the fields in RenderConfig, particulary prompt_prefix, to either String or &str. Alternatively I'd like to learn if there is any particular reason for it only accepting string literals.

Describe alternatives you've considered
I have tried various ways to convert a String to a &'static str but they all fail due to lifetimes. Here, here, and here are some of the stackoverflow questions regarding this. I also tried to concatenate string literals and pass the result, without success. Another method I tried was Box::leak(format!("{}", "Hello world").into_boxed_str()); , but it didn't work, and it's a dirty solution that leaks memory.

Additional context

[mikaelmello]

I see you, I'll figure something out and make it possible!