Support for single page applications route all requests to index.html.
## Problem to Solve
When routing requests to Gitlab Pages, if there is no default index.html, the request renders an error that does not permit SEO or support of SPA on GitLab Pages.
## Solution
Route all requests to GitPages to /index.html by:
* implementing a `route single page app to index.html` to a checkbox in **Pages > Settings**
* Enable SPAs to serve any accompanying files so that it works
* Ensure existing files are served before trying to serve `index.html`
## Update 2021-07-20
Closing this issue in favor of https://gitlab.com/gitlab-org/gitlab-pages/-/issues/57. We aim to enable SPAs via a new `.gitlab-pages.yml`
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