Render descriptions with shared Markdown preview

Use one Markdown presentation for free-form content.

- issue and pull-request descriptions and comments
- milestone and commit descriptions

ios/Sources/Support.swift

@@ -1,5 +1,28 @@
+import MarkdownUI
+import SwiftUI
 import UIKit
 
+struct MarkdownContent: View {
+    let source: String
+
+    var body: some View {
+        Markdown(source)
+            .markdownTheme(.gitHub)
+            .textSelection(.enabled)
+            .frame(maxWidth: .infinity, alignment: .leading)
+    }
+}
+
+@MainActor
+func markdownView(_ source: String) -> UIView {
+    UIHostingConfiguration {
+        MarkdownContent(source: source)
+            .fixedSize(horizontal: false, vertical: true)
+    }
+    .margins(.all, 0)
+    .makeContentView()
+}
+
 func localDate(forUTCTimestamp timestamp: Int64) -> Date {
     var utc = Calendar(identifier: .gregorian)
     utc.timeZone = TimeZone(secondsFromGMT: 0)!
@@ -179,17 +202,6 @@ extension UIColor {
     }
 }
 
-func markdown(_ source: String, textStyle: UIFont.TextStyle = .body) -> NSAttributedString {
-    let attributed = (try? AttributedString(
-        markdown: source,
-        options: .init(interpretedSyntax: .full)
-    )) ?? AttributedString(source)
-    var mutable = attributed
-    mutable.font = .preferredFont(forTextStyle: textStyle)
-    mutable.foregroundColor = UIColor.label
-    return NSAttributedString(mutable)
-}
-
 func configureTextCell(_ cell: UITableViewCell, title: String, detail: String, image: UIImage? = nil) {
     var content = cell.defaultContentConfiguration()
     content.text = title