Add single file audio player, introduce blocks

CHDataManagement/Generator/Blocks/AudioBlockProcessor.swift

@@ -0,0 +1,62 @@
+
+struct AudioBlockProcessor: KeyedBlockProcessor {
+
+    enum Key: String {
+        case name
+        case artist
+        case album
+        case file
+        case cover
+    }
+
+    static let blockId: ContentBlock = .audio
+
+    let content: Content
+    
+    let results: PageGenerationResults
+    
+    let language: ContentLanguage
+    
+    init(content: Content, results: PageGenerationResults, language: ContentLanguage) {
+        self.content = content
+        self.results = results
+        self.language = language
+    }
+
+    func process(_ arguments: [Key : String], markdown: Substring) -> String {
+        guard let name = arguments[.name],
+              let artist = arguments[.artist],
+              let album = arguments[.album],
+              let fileId = arguments[.file],
+              let cover = arguments[.cover] else {
+            invalid(markdown)
+            return ""
+        }
+
+        guard let image = content.image(cover) else {
+            results.missing(file: cover, source: "Audio Block")
+            return ""
+        }
+
+        guard let file = content.file(fileId) else {
+            results.missing(file: fileId, source: "Audio Block")
+            return ""
+        }
+
+        let coverSize = 2 * content.settings.audioPlayer.smallCoverImageSize
+        let coverImage = image.imageVersion(width: coverSize, height: coverSize, type: image.type)
+        let footer = SingleFilePlayer.footer(
+            name: name,
+            artist: artist,
+            album: album,
+            url: file.absoluteUrl,
+            cover: coverImage.outputPath)
+
+        results.require(image: coverImage)
+        results.require(footer: footer)
+        results.require(headers: .audioPlayerJs, .audioPlayerCss)
+        results.require(icons: .audioPlayerPlay, .audioPlayerPause)
+
+        return SingleFilePlayer().content
+    }
+}