render markdown preview in the file browser

mac/Sources/Byre/Files.swift

@@ -225,6 +225,9 @@ private struct FilesBody: View {
         } else if let c = model.content {
             if c.binary {
                 EmptyText(text: "Binary file.")
+            } else if model.place.file?.lowercased().hasSuffix(".md") == true {
+                FileMarkdown(content: c, taskId: store.selectedTaskId, dir: model.place.dir)
+                    .id(model.generation)
             } else {
                 FileText(content: c)
                     .id(model.generation)
@@ -308,6 +311,28 @@ private struct EntryRow: View {
     }
 }
 
+private struct FileMarkdown: View {
+    let content: FileContent
+    let taskId: String?
+    let dir: String
+
+    var body: some View {
+        ScrollView {
+            VStack(alignment: .leading, spacing: 0) {
+                MarkdownView(blocks: parseMarkdown(content.text), ctx: MDContext(taskId: taskId, dir: dir))
+                if content.truncated {
+                    Text("Showing the first \(bytes(shown(content))) of \(bytes(content.size)).")
+                        .foregroundStyle(Palette.muted)
+                        .padding(.top, 12)
+                }
+            }
+            .frame(maxWidth: .infinity, alignment: .leading)
+            .padding(.horizontal, 16)
+            .padding(.vertical, 10)
+        }
+    }
+}
+
 private struct FileText: View {
     let content: FileContent