[feat] update some feature

sync code of  fastrtc,
add text support through datachannel,
fix safari connect problem
support chat without camera or mic

docs/userguide/video.md

@@ -0,0 +1,57 @@
+# Video Streaming
+
+## Input/Output Streaming
+
+We already saw this example in the [Quickstart](../../#quickstart) and the [Core Concepts](../streams) section.
+
+=== "Code"
+    
+    ``` py title="Input/Output Streaming"
+    from fastrtc import Stream
+    import gradio as gr
+
+    def detection(image, conf_threshold=0.3): # (1)
+        processed_frame = process_frame(image, conf_threshold)
+        return processed_frame # (2)
+
+    stream = Stream(
+        handler=detection,
+        modality="video",
+        mode="send-receive", # (3)
+        additional_inputs=[
+            gr.Slider(minimum=0, maximum=1, step=0.01, value=0.3)
+        ],
+    )
+    ```
+
+    1. The webcam frame will be represented as a numpy array of shape (height, width, RGB).
+    2. The function must return a numpy array. It can take arbitrary values from other components.
+    3. Set the `modality="video"` and `mode="send-receive"`
+=== "Notes"
+    1. The webcam frame will be represented as a numpy array of shape (height, width, RGB).
+    2. The function must return a numpy array. It can take arbitrary values from other components.
+    3. Set the `modality="video"` and `mode="send-receive"`
+
+## Server-to-Client Only
+
+In this case, we stream from the server to the client so we will write a generator function that yields the next frame from the video (as a numpy array)
+and set the `mode="receive"` in the `WebRTC` component.
+
+=== "Code"
+    ``` py title="Server-To-Client"
+    from fastrtc import Stream
+
+    def generation():
+        url = "https://download.tsi.telecom-paristech.fr/gpac/dataset/dash/uhd/mux_sources/hevcds_720p30_2M.mp4"
+        cap = cv2.VideoCapture(url)
+        iterating = True
+        while iterating:
+            iterating, frame = cap.read()
+            yield frame
+
+    stream = Stream(
+        handler=generation,
+        modality="video",
+        mode="receive"
+    )
+    ```