Editing Troubleshooting of Azure Cognitive Services API (section)

== How to fix the error: invalid subscription key or wrong API endpoint ==

Error message
: <pre>{"error":{"code":"401","message":"Access denied due to invalid subscription key or wrong API endpoint. Make sure to provide a valid key for an active subscription and use a correct regional API endpoint for your resource."}}</pre>

Solution: 
* Verify the API endpoint URL
* Verify the subscription key and add it to the request header

Example command edited from the API document<ref>[https://docs.microsoft.com/zh-tw/azure/cognitive-services/Computer-vision/quickstarts-sdk/client-library?pivots=programming-language-rest-api&tabs=visual-studio 快速入門：光學字元辨識 (OCR) 用戶端程式庫或 REST API - Azure Cognitive Services | Microsoft Docs]</ref>
<pre>
curl -v -X POST "<API endpoint>" -H "Content-Type: application/json" -H "Ocp-Apim-Subscription-Key: <subscription key>" --data-ascii "{\"url\":\"<image URL>\"}"
</pre>

<pre>
curl -v -X POST "https://westcentralus.api.cognitive.microsoft.com/vision/v3.2/read/analyze" -H "Content-Type: application/json" -H "Ocp-Apim-Subscription-Key: <subscription key>" --data-ascii "{\"url\":\"https://upload.wikimedia.org/wikipedia/commons/thumb/a/af/Atomist_quote_from_Democritus.png/338px-Atomist_quote_from_Democritus.png\"}"
</pre>