Add mascot demo. Update assets for readme

CommandNotch/CommandNotchTests/ScreenRegistryTests.swift

@@ -313,7 +313,12 @@ private final class ScreenRegistryTestSettingsProvider: TerminalSessionConfigura
 
 private struct ScreenRegistryUnusedTerminalSessionFactory: TerminalSessionFactoryType {
     @MainActor
-    func makeSession(fontSize: CGFloat, theme: TerminalTheme, shellPath: String) -> TerminalSession {
+    func makeSession(
+        fontSize: CGFloat,
+        theme: TerminalTheme,
+        shellPath: String,
+        initialDirectory: String?
+    ) -> TerminalSession {
         fatalError("ScreenRegistryTests should not create live terminal sessions.")
     }
 }