use shallow routing for URL persistence. (#139)

* Expose shallow routing as a prop.

* Default shallow to true.

* Shallow push is always enabled.

* Removed shallow from README.md

README.md

@@ -277,7 +277,7 @@ See [atomFamily](https://recoiljs.org/docs/api-reference/utils/atomFamily) for m
 
 #### Return
 
-A function which takes `paramter` that map to an atom, and its `initialValue`.
+A function which takes `parameter` that map to an atom, and its `initialValue`.
 
 #### Example
 

src/url/useSyncURLNext.ts

@@ -31,9 +31,15 @@ export function useSyncURLNext(): Partial<
   }, [])
 
   const browserInterface: BrowserInterface = {
-    replaceURL: useCallback((url: string) => replace(url), [replace]),
+    replaceURL: useCallback(
+      (url: string) => replace(url, undefined, { shallow: true }),
+      [replace]
+    ),
 
-    pushURL: useCallback((url: string) => push(url), [push]),
+    pushURL: useCallback(
+      (url: string) => push(url, undefined, { shallow: true }),
+      [push]
+    ),
 
     getURL: useCallback(() => {
       const url = new URL(