Adds a dev container and Codespaces docs

Signed-off-by: Samruddhi Khandale <samruddhikhandale@github.com>

.devcontainer/setup.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+#   Copyright The containerd Authors.
+
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+
+#       http://www.apache.org/licenses/LICENSE-2.0
+
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+set -eux
+
+script/setup/install-seccomp
+script/setup/install-runc
+script/setup/install-cni $(grep containernetworking/plugins go.mod | awk '{print $2}')
+script/setup/install-critools
+script/setup/install-failpoint-binaries
+script/setup/install-gotestsum
+script/setup/install-teststat
+
+script/setup/install-protobuf \
+    && mkdir -p /go/src/usr/local/bin /go/src/usr/local/include \
+    && mv /usr/local/bin/protoc /go/src/usr/local/bin/protoc \
+    && mv /usr/local/include/google /go/src/usr/local/include/google
+
+make binaries GO_BUILD_FLAGS="-mod=vendor"
+sudo -E PATH=$PATH make install