update docs for new convertmodel website (Tencent#6617)

Author: futz12

.github/ISSUE_TEMPLATE/model-convert.md

@@ -1,6 +1,6 @@
 ---
 name: "\U0001F6B8 model convert issue"
-about: "Life is Short, Use pnnx and convertmodel.com"
+about: "Life is Short, Use pnnx and pnnx.pchar.cn"
 ---
 
 ## error log | 日志或报错信息 | ログ

docs/how-to-use-and-FAQ/use-ncnn-with-pytorch-or-onnx.md

@@ -124,6 +124,8 @@ For users who already have an `.onnx` file, please use pnnx for conversion.
 
 *   **Method 2 (Alternative):** For non-Python environments or to use a standalone program, you can download the latest executable from the [pnnx Releases page](https://github.com/pnnx/pnnx/releases).
 
+*    **Method 3 (Convert Everywhere with GUI):** To convert models to ncnn anytime and anywhere, you can use [pnnx.js](https://pnnx.pchar.cn). To protect your data security, the website is built based on wasm64 technology, and your models will not be uploaded to the server.
+
 ### 2. Run the Command-Line Conversion
 
 Open a terminal, navigate to the directory containing your model file, and run the following command.