Add data model links to various places where it was marked WIP (#1668)

Co-authored-by: Armin Ruech <[email protected]>

Author: jsuereth

README.md

@@ -42,6 +42,8 @@ Technical committee holds regular meetings, notes are held
 - Data Specification
   - [Semantic Conventions](specification/overview.md#semantic-conventions)
   - [Protocol](specification/protocol/README.md)
+    - [Metrics](specification/metrics/datamodel.md)
+    - [Logs](specification/logs/data-model.md)
 - About the Project
   - [Timeline](#project-timeline)
   - [Notation Conventions and Compliance](#notation-conventions-and-compliance)

specification/metrics/README.md

@@ -30,7 +30,7 @@ Table of Contents
 * [Specifications](#specifications)
   * [Metrics API](./api.md)
   * Metrics SDK (not available yet)
-  * Metrics Data Model and Protocol (not available yet)
+  * [Metrics Data Model and Protocol](datamodel.md)
   * [Semantic Conventions](./semantic_conventions/README.md)
 
 </details>
@@ -108,7 +108,7 @@ SDK](../overview.md#sdk) concept concept for more information.
 
 * [Metrics API](./api.md)
 * Metrics SDK (not available yet)
-* Metrics Data Model and Protocol (not available yet)
+* [Metrics Data Model and Protocol](datamodel.md)
 * [Semantic Conventions](./semantic_conventions/README.md)
 
 ## References