manifest: support time-based patch history

[This](https://conda.discourse.group/t/how-we-reduced-condas-index-fetch-bandwidth-by-99/257) kind of thing could significantly reduce download requirements for users accessing the store, especially as our number of extensions scales up. Much easier to scale fast if the appropriate infrastructure has been designed in from early on :-)

Patch history is already possible to some extent with the git history of the `gh-pages` branch, especially if we enforce an ordering for the extensions and versions, but a content-aware JSON patch history could likely be a fair amount more efficient.

Comienza con el historial de la rama gh-pages y el orden de extensiones/versiones mencionado en el issue. Investiga cómo podría encajar un historial de parches JSON consciente del contenido en el store existente, y define done como admitir la recuperación de parches basada en el tiempo mientras se reducen los requisitos de descarga.

Escrito por el modelo de indexación a partir del texto del issue.