Added toasts redux for alerts

• Added:
- toasts redux for alerts

app/javascript/gabsocial/reducers/toasts.js

@@ -0,0 +1,25 @@
+import {
+  TOAST_SHOW,
+  TOAST_DISMISS,
+  TOAST_CLEAR,
+} from '../actions/toasts'
+import { Map as ImmutableMap, List as ImmutableList } from 'immutable'
+
+const initialState = ImmutableList([])
+
+export default function toasts(state = initialState, action) {
+  switch(action.type) {
+  case TOAST_SHOW:
+    return state.push(ImmutableMap({
+      key: state.size > 0 ? state.last().get('key') + 1 : 0,
+      message: action.message,
+      type: action.toastType,
+    }))
+  case TOAST_DISMISS:
+    return state.filterNot(item => item.get('key') === action.toast.key)
+  case TOAST_CLEAR:
+    return state.clear()
+  default:
+    return state
+  }
+}