[bug] Childpages outside of rootPage model json don't render with SPA 2.0

**Describe the bug**
Before SPA 2.0, once the ModelManager recognizes there is root page configured, it retrieves the model.json along with other child pages, if the user clicks on a link that points to another page that's not available in the initial load, it will request the model.json and eventually render that page too. With SPA 2.0, that behavior is lost

**Package version**
2.0.x

**To Reproduce**
Steps to reproduce the behavior:
1. Use the WKND SPA app from React/latest branch, and install the same on AEM
2. Launch the app either inside AEM using wcmmode=disabled or run the app locally on 3000 port
3. From the hamburger navigation, click on Page 3, it loads fine even though the initial json doesn't contain this page
4. Now use the React/2.0.0 branch, and install the same on AEM
5. Launch the app in the same way as earlier
6. Now you will see a blank screen when you click on Page 3 from hamburger navigation

**Expected behavior**
Behavior should be consistent with v1.x implementation as this is a very basic usecase, and shouldn't force us to write a custom implementation. Alternatively a hook or a helper to accomplish the same is also fine i.e. similar to withModel wrapper we had in v1.x

**Screenshots**
If applicable, add screenshots to help explain your problem.

Expected behavior and working behavior both locally & on AEM (Open Home Page, click on Page 3 link of hamburger menu)
Note: Only screenshot of local app is shared. Didn't share AEM app screenshot as we know it works before SPA 2.0

Changed behavior in SPA 2.0
Note: Only screenshot of AEM app is shared, Can share local app screenshot if required.

**Additional context**
Add any other context about the problem here.