Add "error" option to resource level BotKube config

[PrasadG193]

Is your feature request related to a problem? Please describe.
As of now, if someone is interested in getting only error/failure events for particular resources, he/she has to add following configuration in BotKube:

  ## Resources you want to watch
  resources:
    - name: NAME_OF_THE_RESOURCE  
      namespaces: 
        - all

  # K8S error/warning events you want to receive for the configured resources
  events:
    types:
      - warning

This is quite difficult to read and understand. There should be an easier way to configure this.

Describe the solution you'd like
Instead of having events as a separate field in the BotKube configuration, we should have error as a additional field at resource level configuration

  ## Resources you want to watch
  resources:
    - name: NAME_OF_THE_RESOURCE  
      namespaces: 
        - all
      events:
        - create
        - update
        - delete
        - error