Apply Mastodon's link truncation

Closes #344

Tusker/HTMLConverter.swift

@@ -55,7 +55,21 @@ struct HTMLConverter {
         case let node as Element:
             let attributed = NSMutableAttributedString(string: "", attributes: [.font: font, .foregroundColor: color])
             for child in node.getChildNodes() {
+                var appendEllipsis = false
+                if node.tagName() == "a",
+                   let el = child as? Element {
+                    if el.hasClass("invisible") {
+                        continue
+                    } else if el.hasClass("ellipsis") {
+                        appendEllipsis = true
+                    }
+                }
+                
                 attributed.append(attributedTextForHTMLNode(child, usePreformattedText: usePreformattedText || node.tagName() == "pre"))
+                
+                if appendEllipsis {
+                    attributed.append(NSAttributedString("…"))
+                }
             }
             
             switch node.tagName() {