Add OT Trace Propagator. (#1402)

* Add OT Trace propagator note.

* Add a further note.

* Update specification/context/api-propagators.md

Co-authored-by: Diego Hurtado <ocelotl@users.noreply.github.com>

* Update specification/context/api-propagators.md

Co-authored-by: Diego Hurtado <ocelotl@users.noreply.github.com>

* Update specification/context/api-propagators.md

Co-authored-by: Yuri Shkuro <yurishkuro@users.noreply.github.com>

Co-authored-by: Diego Hurtado <ocelotl@users.noreply.github.com>
Co-authored-by: Bogdan Drutu <lazy@splunk.com>
Co-authored-by: Yuri Shkuro <yurishkuro@users.noreply.github.com>
Co-authored-by: Bogdan Drutu <bogdandrutu@gmail.com>

specification/context/api-propagators.md

@@ -330,6 +330,13 @@ organization and MUST be distributed as OpenTelemetry extension packages:
 * [B3](https://github.com/openzipkin/b3-propagation).
 * [Jaeger](https://www.jaegertracing.io/docs/latest/client-libraries/#propagation-format).
 
+This is a list of additional propagators that MAY be maintained and distributed
+as OpenTelemetry extension packages:
+
+* [OT Trace](https://github.com/opentracing?q=basic&type=&language=). Propagation format
+  used by the OpenTracing Basic Tracers. It MUST NOT use `OpenTracing` in the resulting
+  propagator name as it is not widely adopted format in the OpenTracing ecosystem.
+
 Additional `Propagator`s implementing vendor-specific protocols such as AWS
 X-Ray trace header protocol MUST NOT be maintained or distributed as part of
 the Core OpenTelemetry repositories.