`Notes Reducer uses previous state anf object.  
  Takes in Action/ Undefined 
    Gets Previous State and Action 
    First Agrument into Reducer is always going to be returned the last time it was ran 
    only change is ACTION OBJECT 
    Reducers are PURE- huh? 
      anytime we call reducer we are not suppose to do anything else like dom, API etc. 
    when reducer gets call it just get action and value
    do computation with state and action 
     (* DO NOT MUTATE STATE EVER* ) 
       See Above . use spread op, etc instead of mutating state directly.`

   
          export defualt (state = [], action ) => {
            switch(action.type){
              case 'FETCH_POST':
                return action.payload
              default:
                return state; 
            }
          };