Adding nextjs + 11labs + openai streaming demo (#139)

* adding nextjs + 11labs + openai streaming demo

* removing package-lock

demo/nextjs_voice_chat/frontend/fastrtc-demo/components/theme-provider.tsx

@@ -0,0 +1,101 @@
+"use client";
+
+import { createContext, useContext, useEffect, useState } from "react";
+
+type Theme = "light" | "dark" | "system";
+
+type ThemeProviderProps = {
+  children: React.ReactNode;
+  defaultTheme?: Theme;
+  storageKey?: string;
+  attribute?: string;
+  enableSystem?: boolean;
+  disableTransitionOnChange?: boolean;
+};
+
+type ThemeProviderState = {
+  theme: Theme;
+  setTheme: (theme: Theme) => void;
+};
+
+const initialState: ThemeProviderState = {
+  theme: "system",
+  setTheme: () => null,
+};
+
+const ThemeProviderContext = createContext<ThemeProviderState>(initialState);
+
+export function ThemeProvider({
+  children,
+  defaultTheme = "system",
+  storageKey = "theme",
+  attribute = "class",
+  enableSystem = true,
+  disableTransitionOnChange = false,
+  ...props
+}: ThemeProviderProps) {
+  const [theme, setTheme] = useState<Theme>(defaultTheme);
+
+  useEffect(() => {
+    const savedTheme = localStorage.getItem(storageKey) as Theme | null;
+    
+    if (savedTheme) {
+      setTheme(savedTheme);
+    } else if (defaultTheme === "system" && enableSystem) {
+      const systemTheme = window.matchMedia("(prefers-color-scheme: dark)").matches
+        ? "dark"
+        : "light";
+      setTheme(systemTheme);
+    }
+  }, [defaultTheme, storageKey, enableSystem]);
+
+  useEffect(() => {
+    const root = window.document.documentElement;
+    
+    if (disableTransitionOnChange) {
+      root.classList.add("no-transitions");
+      
+      // Force a reflow
+      window.getComputedStyle(root).getPropertyValue("opacity");
+      
+      setTimeout(() => {
+        root.classList.remove("no-transitions");
+      }, 0);
+    }
+    
+    root.classList.remove("light", "dark");
+    
+    if (theme === "system" && enableSystem) {
+      const systemTheme = window.matchMedia("(prefers-color-scheme: dark)").matches
+        ? "dark"
+        : "light";
+      root.classList.add(systemTheme);
+    } else {
+      root.classList.add(theme);
+    }
+
+    localStorage.setItem(storageKey, theme);
+  }, [theme, storageKey, enableSystem, disableTransitionOnChange]);
+
+  const value = {
+    theme,
+    setTheme: (theme: Theme) => {
+      setTheme(theme);
+    },
+  };
+
+  return (
+    <ThemeProviderContext.Provider {...props} value={value}>
+      {children}
+    </ThemeProviderContext.Provider>
+  );
+}
+
+export const useTheme = () => {
+  const context = useContext(ThemeProviderContext);
+
+  if (context === undefined)
+    throw new Error("useTheme must be used within a ThemeProvider");
+
+  return context;
+};