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/Registry.cs

@@ -0,0 +1,42 @@
+// *** 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 Registry
+    {
+        /// <summary>
+        /// The registry's address (e.g. "docker.io").
+        /// </summary>
+        public readonly string Address;
+        /// <summary>
+        /// Password or token for the registry.
+        /// </summary>
+        public readonly string? Password;
+        /// <summary>
+        /// Username for the registry.
+        /// </summary>
+        public readonly string? Username;
+
+        [OutputConstructor]
+        private Registry(
+            string address,
+
+            string? password,
+
+            string? username)
+        {
+            Address = address;
+            Password = password;
+            Username = username;
+        }
+    }
+}