Move Collector adopters to project-wide file (#394)

* Move Collector adopters to project-wide file

* Update ADOPTERS.md

ADOPTERS.md

@@ -2,4 +2,16 @@
 
 A non-exhaustive unordered list of organizations that have adopted OpenTelemetry.
 
-**_[Google Cloud Platform](https://cloud.google.com)_** uses the OpenTelemetry collector as an agent and forwarder. Cloud Trace and Monitoring use the OpenTelemetry SDKs to capture metrics and traces from customers' applications.
+[AppDirect](https://www.appdirect.com/)
+
+[Google Cloud Platform](https://cloud.google.com) uses the OpenTelemetry collector as an agent and forwarder. Cloud Trace and Monitoring use the OpenTelemetry SDKs to capture metrics and traces from customers' applications.
+
+[Grafana Labs](https://grafana.com/)
+
+[OrderMyGear](https://www.ordermygear.com/)
+
+[Shopify](https://www.shopify.com/)
+
+[Splunk](https://www.splunk.com/)
+
+[Wandera](https://www.wandera.com/)