Added pricing calculator to TOC

Author: oliver scholz

articles/cognitive-services/Speech-Service/toc.yml

@@ -547,6 +547,8 @@
       href: sovereign-clouds.md
     - name: Pricing and limits
       href: https://azure.microsoft.com/pricing/details/cognitive-services/speech-services/
+    - name: Pricing calculator
+      href: https://azure.microsoft.com/pricing/calculator/#cognitive-services
     - name: Compliance
       href: https://azure.microsoft.com/support/legal/cognitive-services-compliance-and-privacy/
     - name: Encryption