docs: add error-codes content

docs/docs/quickstart/error-codes/_category_.json

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+{
+  "label": "Error Codes",
+  "position": 7,
+  "link": {
+    "type": "generated-index",
+    "description": "List of Error Codes for Jan users"
+  }
+}

docs/docs/quickstart/error-codes/permission-denied.mdx

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+---
+sidebar_position: 1
+---
+
+# Permission Denied
+
+When running Jan, you might encounter the following error message:
+
+```
+Uncaught (in promise) Error: Error invoking layout-480796bff433a3a3.js:538 remote method 'installExtension':
+Error Package /Applications/Jan.app/Contents/Resources/app.asar.unpacked/pre-install/janhq-assistant-extension-1.0.0.tgz does not contain a valid manifest:
+Error EACCES: permission denied, mkdtemp '/Users/username/.npm/_cacache/tmp/ueCMn4'
+```
+
+This error mainly caused by permission problem during installation. To resolve this issue, follow these steps:
+
+1. Open your terminal.
+
+2. Execute the following command to change ownership of the `~/.npm` directory to the current user:
+
+```sh
+sudo chown -R $(whoami) ~/.npm
+```
+
+This command ensures that the necessary permissions are granted for Jan installation, resolving the encountered error.

docs/docs/quickstart/error-codes/something-amiss.mdx

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+---
+sidebar_position: 4
+---
+
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
+# Something's Amiss
+
+When you start a chat with a model and encounter with a Something's Amiss error, here's how to resolve it:
+1. Ensure your OS is up to date.
+2. Choose a model smaller than 80% of your hardware's V/RAM. For example, on an 8GB machine, opt for models smaller than 6GB.
+3. Install the latest [Nightly release](https://jan.ai/install/nightly/) or [clear the application cache](https://jan.ai/troubleshooting/stuck-on-broken-build/) when reinstalling Jan.
+4. Confirm your V/RAM accessibility, particularly if using virtual RAM.
+5. Nvidia GPU users should download [CUDA](https://developer.nvidia.com/cuda-downloads).
+6. Linux users, ensure your system meets the requirements of gcc 11, g++ 11, cpp 11, or higher. Refer to this [link](https://jan.ai/guides/troubleshooting/gpu-not-used/#specific-requirements-for-linux) for details.
+7. You might use the wrong port when you [check the app logs](https://jan.ai/troubleshooting/how-to-get-error-logs/) and encounter the Bind address failed at 127.0.0.1:3928 error. To check the port status, try use the `netstat` command, like the following:
+
+<Tabs>
+    <TabItem value="mac" label="MacOS" default>
+        ```sh
+        netstat -an | grep 3928
+        ```
+    </TabItem>
+    <TabItem value="windows" label="Windows" default>
+        ```sh
+        netstat -ano | find "3928" 
+        tasklist /fi "PID eq 3928"
+        ```
+    </TabItem>
+    <TabItem value="linux" label="Linux" default>
+        ```sh
+        netstat -anpe | grep "3928" 
+        ```
+    </TabItem>
+</Tabs>
+
+:::note
+
+`Netstat` displays the contents of various network-related data structures for active connections
+
+:::
+
+:::tip
+
+Jan uses the following ports:
+
+- Nitro: `3928`
+- Jan API Server: `1337`
+- Jan Documentation: `3001`
+
+:::

docs/docs/quickstart/error-codes/undefined-issue.mdx

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+---
+sidebar_position: 3
+---
+
+# Undefined Issue
+
+Encountering an "undefined" issue in Jan is caused by errors related to the Nitro tool or other internal processes. It can be resolved through the following steps:
+
+1. Clearing the Jan folder and then reopen the application to determine if the problem persists
+2. Manually run the nitro tool located at `~/jan/extensions/@janhq/inference-nitro-extensions/dist/bin/(your-os)/nitro` to check for error messages.
+3. Address any nitro error messages that are identified and reassess the persistence of the issue.
+4. Reopen Jan to determine if the problem has been resolved after addressing any identified errors.
+5. If the issue persists, please share the [app logs](https://jan.ai/troubleshooting/how-to-get-error-logs/) via [Jan Discord](https://discord.gg/mY69SZaMaC) for further assistance and troubleshooting.

docs/docs/quickstart/error-codes/unexpected-token.mdx

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+---
+sidebar_position: 2
+---
+
+# Unexpected Token
+
+Encountering the error `Unexpected token '<', "<!DOCTYPE"...is not valid JSON` when initiating a chat with OpenAI models can be addressed through the following steps:
+
+1. Obtain an OpenAI API key from [OpenAI's developer platform](https://platform.openai.com/) and integrate it into your application.
+
+2. Trying a VPN could potentially solve the issue, especially if it's related to region locking for accessing OpenAI services. By connecting through a VPN, you may bypass such restrictions and successfully initiate chats with OpenAI models.
+
+By following these steps, you can effectively resolve the "Unexpected Token" error and seamlessly start chats with OpenAI models.