Bulk OG image downloader

Pages go out only when you press Extract images, one GET through this project's capped proxy, about 3 seconds apart. The proxy never follows redirects, refuses private addresses, and hands back at most the first 4,096 characters of each page, so pages that put their meta tags after that cut read as no preview image. Preview images load in this tab for measuring; hosts that allow cross-origin reads are re-encoded as PNG into the zip with the manifest, and the rest open in a tab instead. Preview images belong to their owners, so download only what you own or have permission to use.