This change motivated by:noelforte/eleventy-plugin-vento#221

I couldn't figure out why the i18n plugin's presence was breaking thegetNextCollectionItem andgetPreviousCollectionItem filters since the Vento template engine plugin doesn't do anything fancy with the filters.

After a lot of trial and error, I discovered that this search for collections.all at the very end of theGetLocaleCollectionItem module checks a lot of things specific to Eleventy's own internal engines but of course custom engines don't add actx orcontext object, or eventhis.collections, sincethis.page andthis.eleventy are the only context keys Eleventy supports, andcollections is already accessible in page data anyway.

Rather than addthis.collections to the Vento custom engine, could we simplify theall declaration to search thedata key instead since thedata key is already available on the render context anyway?

If not, I can look into addingthis.collections to the custom engine for my plugin, but if this can be handled upstream that puts less pressure on custom engines to support adding it.

Thanks Zach!