Move type ThunkFunction to src/store.ts

Moving in preparation for using this type for the measurements
thunk functions as well.

I had considered adding a new `src/actions/types.ts` file, but that
will be confusing with the action types in `src/actions/types.js`.

src/actions/tree.ts

@@ -13,17 +13,14 @@ import { warningNotification } from "./notifications";
 import { calcFullTipCounts, calcTipCounts } from "../util/treeCountingHelpers";
 import { PhyloNode } from "../components/tree/phyloTree/types";
 import { Metadata } from "../metadata";
-import { AppDispatch, RootState } from "../store";
+import { ThunkFunction } from "../store";
 import { ReduxNode, TreeState } from "../reducers/tree/types";
 
 type RootIndex = number | undefined
 
 /** [root idx tree1, root idx tree2] */
 export type Root = [RootIndex, RootIndex]
 
-/** A function to be handled by redux (thunk) */
-type ThunkFunction = (dispatch: AppDispatch, getState: () => RootState) => void
-
 /**
  * Updates the `inView` property of nodes which depends on the currently selected
  * root index (i.e. what node the tree is zoomed into).

src/store.ts

@@ -54,4 +54,7 @@ if (process.env.NODE_ENV !== 'production' && module.hot) {
 export type RootState = ReturnType<typeof store.getState>
 export type AppDispatch = typeof store.dispatch
 
+/** A function to be handled by redux (thunk) */
+export type ThunkFunction = (dispatch: AppDispatch, getState: () => RootState) => void
+
 export default store;