Add custom #nostr and #coffeechain hashtags

Changelog-Added: Custom hashtags for #nostr and #coffeechain

damus/Util/Hashtags.swift

@@ -0,0 +1,60 @@
+//
+//  Hashtags.swift
+//  damus
+//
+//  Created by William Casarin on 2023-04-06.
+//
+
+import Foundation
+import SwiftUI
+
+struct CustomHashtag {
+    let name: String
+    let color: Color?
+    
+    init(name: String, color: Color? = nil) {
+        self.name = name
+        self.color = color
+    }
+    
+    static let coffee = CustomHashtag(name: "coffee", color: DamusColors.brown)
+    static let bitcoin = CustomHashtag(name: "bitcoin", color: Color.orange)
+    static let nostr = CustomHashtag(name: "nostr", color: DamusColors.purple)
+}
+
+
+let custom_hashtags: [String: CustomHashtag] = [
+    "bitcoin": CustomHashtag.bitcoin,
+    "nostr": CustomHashtag.nostr,
+    "coffee": CustomHashtag.coffee,
+    "coffeechain": CustomHashtag.coffee,
+]
+
+func hashtag_str(_ htag: String) -> CompatibleText {
+    var attributedString = AttributedString(stringLiteral: "#\(htag)")
+    attributedString.link = URL(string: "damus:t:\(htag)")
+    
+    let lowertag = htag.lowercased()
+    
+    var text = Text(attributedString)
+    if let custom_hashtag = custom_hashtags[lowertag] {
+        if let col = custom_hashtag.color {
+            attributedString.foregroundColor = col
+        }
+        
+        let name = custom_hashtag.name
+        
+        text = Text(attributedString)
+        if let img = UIImage(named: "\(name)-hashtag") {
+            attributedString = attributedString + " "
+            attributed_string_attach_icon(&attributedString, img: img)
+        }
+        let img = Image("\(name)-hashtag")
+        text = text + Text(" \(img)")
+    } else {
+        attributedString.foregroundColor = DamusColors.purple
+    }
+    
+    return CompatibleText(text: text, attributed: attributedString)
+ }
+