feat: add loadNavbarOnCover configuration

[sy-records]

Summary

resolve #1375

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[anikethsaha]

One change, other than that, LGTM

[Koooooo-7]

Little problem.
Steps:

1. set loadNavbarOnCover: false,.
2. clink to another selection.
3. clink the back button of the browser, it will back to the cover page.
   the nav will show on the cover now.

[sy-records]

This is caused by not reloading the page, I think that's acceptable.
It just doesn't show up when you visit the home page directly.

[Koooooo-7]

This is caused by not reloading the page, I think that's acceptable.
It just doesn't show up when you visit the home page directly.

It make no sense, there is no reason to make an element visible, which had been set not show.
There is one way I found to make it, FYR.

    // Load nav
    if (loadNavbar) {
      // default show the nav
      document.querySelector('.app-nav').style.display = 'inline';
      if (path === '/' && !loadNavbarOnCover) {
        // hidden nav on cover
        document.querySelector('.app-nav').style.display = 'none';
        return;
      }

Maybe you could get another brilliant one :).

[Koooooo-7]

Well.
I think the test is not a test actually， it just check the configuration property exist, not checking if it works tho.

Besides that, I think we need concern about refactoring the nav, for some reason. #1230