feat: introduce OFREP to appendix section (#246)

## This PR

Introduce OpenFeature Remote Evaluation Protocol(OFREP) as an appendix
with minimal details for visibility.

---------

Signed-off-by: Kavindu Dodanduwa <kavindudodanduwa@gmail.com>
Signed-off-by: Kavindu Dodanduwa <Kavindu-Dodan@users.noreply.github.com>
Co-authored-by: Todd Baert <todd.baert@dynatrace.com>
Co-authored-by: Michael Beemer <beeme1mr@users.noreply.github.com>

Author: 3 people

specification/appendix-c-ofrep.md

@@ -0,0 +1,19 @@
+---
+id: appendix-c
+title: "Appendix C: OpenFeature Remote Evaluation Protocol"
+description: A unified protocol for feature flagging
+sidebar_position: 5
+---
+
+# Appendix C: OpenFeature Remote Evaluation Protocol
+
+OpenFeature Remote Evaluation Protocol (OFREP) is a unified feature flag evaluation protocol that adheres to the OpenFeature semantics.
+You can find proposals, discussions and the progress at the dedicated [OpenFeature OFREP](https://github.com/open-feature/protocol) repository.
+
+There is a dedicated [OpenFeature working group](https://github.com/open-feature/community/blob/main/config/open-feature/spec-evaluation/workgroup.yaml) for this initiative that focuses on:
+
+- Feature flag evaluation protocol
+- Telemetry enrichment of the evaluations
+- Reference implementations of the protocol
+
+If you are interested in this initiative, you can join the [`#openfeature-remote-evaluation-protocol`](https://cloud-native.slack.com/archives/C066A48LK35) Slack channel on the [CNCF Slack](https://communityinviter.com/apps/cloud-native/cncf) workspace.