Customized VIM status prompt and css class

[SPiCaRiA]

Describe the feature that you'd like:
Currently, the VIM status prompt is done with hardcoded switch among the vimStatus enum of emojis. This is very different from the VIM behavior that most people are used to, and it would be a game changing thing to leave a door for customizing it.

Additional context:
Possible solutions:

1. Short-term (serves people who write CSS):
   Add CSS classes to the div element corresponding to current status (e.g. .plugin-vimrc-vim-status-normal). This will allow users writing their own dirty CSS snippets to overwrite the prompt string with pseudo elements.
2. Long-term (serves everyone):
   Add a plug-in setting to customize the text content. However, I still strongly recommend adding the CSS classes, just for more flexibility (e.g. colored text).