Setup links and sources to serve from non-root URL

Currently, all of the landscape app links and sources are absolute paths from the root of the URL. For example, a logo is pulled from `/logos/mylogo.svg`. This works fine if you are hosting from the root (e.g. `https://landscape.cncf.io`). However, if a user creates a landscape and attempts to host it from `https://my.org/landscape/`, the links and source are broken. The logo source would be `https://my.org/logos/mylogo.svg`, but it sits at `https://my.org/landscape/logos/mylogo.svg` on the server.

Can you make the links relative to `index.html` rather than absolute?