Add roadmap file

Signed-off-by: Jia Zhang <zhang.jia@linux.alibaba.com>

ROADMAP.md

+# Inclavare Containers Roadmap
+
+This document provides the roadmap of Inclavare Containers project.
+
+## rune
+
+- Code refactoring for minimizing the dependency on libcontainer. 
+- Leave this CLI to using docker.
+
+## libenclave
+
+- Implement Enclave VMM to launch the enclave in form of confidential VM based on vSGX, SEV and TDX technologies.
+
+## shim-rune
+
+- Integrate libenclave and libcontainer. 
+
+## Enclave Runtime
+
+- Support more enclave runtimes such as [WAMR](https://github.com/bytecodealliance/wasm-micro-runtime), [sgx-lkl](https://github.com/lsds/sgx-lkl), [enarx](https://github.com/enarx/enarx), [openenclave](https://github.com/openenclave/openenclave) and so on.
+- Provide a reference Enclave OS for confidential VM. 
+
+## Enclave Pooling Manager
+
+- Implement bundle cache and enclave pooling for dramatically speeding up enclave launch time.
+
+## Enclave Attestation Infrastructure
+
+- Implement general attestation service and infrastructure for confidential Kubernetes.