Add script and instruction to build all the docker images by yourself

contrib/DockerFileBuildHelper/Image.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Text.RegularExpressions;
+
+namespace DockerFileBuildHelper
+{
+    public class Image
+    {
+        public string User { get; private set; }
+        public string Name { get; private set; }
+        public string Tag { get; private set; }
+
+        public string DockerHubLink
+        {
+            get
+            {
+                return User == string.Empty ?
+                    $"https://hub.docker.com/_/{Name}" :
+                    $"https://hub.docker.com/r/{User}/{Name}";
+            }
+        }
+
+        public static Image Parse(string str)
+        {
+            //${BTCPAY_IMAGE: -btcpayserver / btcpayserver:1.0.3.21}
+            var variableMatch = Regex.Match(str, @"\$\{[^-]+-([^\}]+)\}");
+            if(variableMatch.Success)
+            {
+                str = variableMatch.Groups[1].Value;
+            }
+            Image img = new Image();
+            var match = Regex.Match(str, "([^/]*/)?([^:]+):?(.*)");
+            if (!match.Success)
+                throw new FormatException();
+            img.User = match.Groups[1].Length == 0 ? string.Empty : match.Groups[1].Value.Substring(0, match.Groups[1].Value.Length - 1);
+            img.Name = match.Groups[2].Value;
+            img.Tag = match.Groups[3].Value;
+            if (img.Tag == string.Empty)
+                img.Tag = "latest";
+            return img;
+        }
+
+        public override string ToString()
+        {
+            StringBuilder builder = new StringBuilder();
+            if (!String.IsNullOrWhiteSpace(User))
+                builder.Append($"{User}/");
+            builder.Append($"{Name}");
+            if (!String.IsNullOrWhiteSpace(Tag))
+                builder.Append($":{Tag}");
+            return builder.ToString();
+        }
+    }
+}