Fix infinite scrolling of results on search page

[e-five256]

infinite scrolling on the search page currently does not work, throwing the javascript exception of invalid json and showing the paginator instead. this updates the controller to handle xml requests

(this might sound familiar, it also isn't working by the same mechanic on user pages so expect that some time in the future)

based on similar work Benti did to get infinite scrolling working on tag pages

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marked as draft as although I am getting the next page results, seeing some stuff missing. might've just messed up bringing the code over for this as it's a bit unique (can show a magazine box or user box or threads or microblogs etc). but almost thought I accidentally lost my changes so just wanted to get them up before I risk losing my work so far

[github-actions[bot]]

This PR is stale because it has been open 40 days with no activity.