Generate open graph meta tags

CHDataManagement/Model/FileResource.swift

@@ -246,6 +246,20 @@ final class FileResource: Item, LocalizedItem {
         .init(image: self, type: type, maximumWidth: width, maximumHeight: height)
     }
 
+    func linkPreviewImage(results: PageGenerationResults) -> String {
+        let type: FileType
+        switch self.type {
+        case .jpg, .png, .gif: type = self.type
+        default: type = .jpg
+        }
+        let version = imageVersion(
+            width: content.settings.general.linkPreviewImageWidth,
+            height: content.settings.general.linkPreviewImageHeight,
+            type: type)
+        results.require(image: version)
+        return content.settings.general.url + version.outputPath
+    }
+
     // MARK: Paths
 
     func removeFileFromOutputFolder() {