[bug] Support of alias and Sling Mappings

**Describe the bug**
It seems like sling:alias and mappings are not supported with AEM SPA.
I don't know if this ticket should be rather a feature request than a bug ticket but as it is core functionality in AEM I reported it as a bug.

**Package version**
All version

**To Reproduce**
Steps to reproduce the behavior:
1. Add Sling alias on any SPA page. For my example I installed https://github.com/adobe/aem-guides-wknd-spa and add an alias on the homepage http://localhost:4502/editor.html/content/wknd-spa-react/us/en/home.html
2. Open the homepage with the alias http://localhost:4502/content/wknd-spa-react/us/en/alias.html?wcmmode=disabled
3. See that no data is rendered

**Expected behavior**
Data should still be rendered.

**Screenshots**
Not applicable

**Additional context**
This has been reported as a ticket in the archived repo https://github.com/adobe/aem-spa-project-archetype/issues/86 but it was never closed.

Start by reproducing the issue with the WKND SPA homepage, an added Sling alias, and the provided wcmmode=disabled URL; also review the archived aem-spa-project-archetype issue. Done means the SPA page data renders when accessed through its alias and Sling mappings, with equivalent coverage for the reported mapping case.

Written by the indexing model from the issue text.