add package.go file to use compose-go in docker cli

Signed-off-by: Guillaume Lours <[email protected]>

package.go

@@ -0,0 +1,21 @@
+/*
+   Copyright 2020 The Compose Specification 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.
+*/
+
+/*
+Go reference library for parsing and loading Compose files as specified by the
+Compose specification https://github.com/compose-spec/compose-spec.
+*/
+package compose // import "github.com/compose-spec/compose-go"