Move theme settings from config.toml to themes config

[sigmaSd]

These settings https://github.com/sigmaSd/IRust/blob/master/crates/irust/src/irust/options.rs#L11-L24 https://github.com/sigmaSd/IRust/blob/master/crates/irust/src/irust/options.rs#L33-L34 I think belong to the themes config

I think its better to move them and the theme configuration would look something like

[rust]
keyword = 
keyword2 = 
...
[irust]
welcome_msg =
input_prompt =
input_color = 
...