feat: Presets (pre-built configurations with widgets)

[vmarcosp]

Since the configurations are simply objects exported and read by the CLI, we could offer pre-built configurations with various options for the status bar (left), window management, theming, and more.

import { minimal } from 'better-tmux/presets''

export default minimal

Customizing:

import { minimal } from 'better-tmux/presets'

export default {
  ...minimal, 
  theme: 'nord'
}