Initial provider implementation (#18)

This brings over the initial buildx prototype from pulumi/pulumi-docker
and fixes various build and release issues.

sdk/dotnet/Outputs/ExportLocal.cs

@@ -0,0 +1,27 @@
+// *** WARNING: this file was generated by pulumi. ***
+// *** Do not edit by hand unless you're certain you know what you are doing! ***
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Threading.Tasks;
+using Pulumi.Serialization;
+
+namespace Pulumi.DockerBuild.Outputs
+{
+
+    [OutputType]
+    public sealed class ExportLocal
+    {
+        /// <summary>
+        /// Output path.
+        /// </summary>
+        public readonly string Dest;
+
+        [OutputConstructor]
+        private ExportLocal(string dest)
+        {
+            Dest = dest;
+        }
+    }
+}