Add clear image cache button in settings

Closes: #260
Changelog-Added: Added clear cache button to wipe pfp/image cache

damus/Views/ConfigView.swift

@@ -6,6 +6,7 @@
 //
 import AVFoundation
 import SwiftUI
+import Kingfisher
 
 struct ConfigView: View {
     let state: DamusState
@@ -113,6 +114,14 @@ struct ConfigView: View {
                     }
                 }
                 
+                Section("Clear Cache") {
+                    Button("Clear") {
+                        KingfisherManager.shared.cache.clearMemoryCache()
+                        KingfisherManager.shared.cache.clearDiskCache()
+                        KingfisherManager.shared.cache.cleanExpiredDiskCache()
+                    }
+                }
+                
                 Section("Reset") {
                     Button("Logout") {
                         confirm_logout = true