Add a reliable version and integrate libsonnet definition

docker/Dockerfile.windows.1803

@@ -1,5 +1,5 @@
 # escape=`
-FROM plugins/base:windows-amd64
+FROM plugins/base:windows-1803
 
 LABEL maintainer="Drone.IO Community <drone-dev@googlegroups.com>" `
   org.label-schema.name="Drone NPM" `

docker/Dockerfile.windows.1809

@@ -0,0 +1,12 @@
+# escape=`
+FROM plugins/base:windows-1809
+
+LABEL maintainer="Drone.IO Community <drone-dev@googlegroups.com>" `
+  org.label-schema.name="Drone NPM" `
+  org.label-schema.vendor="Drone.IO Community" `
+  org.label-schema.schema-version="1.0"
+
+# TODO: install required tools
+
+ADD release\drone-npm.exe c:\drone-npm.exe
+ENTRYPOINT [ "c:\\drone-npm.exe" ]

docker/manifest.tmpl

@@ -24,8 +24,14 @@ manifests:
       os: linux
       variant: v7
   -
-    image: plugins/npm:{{#if build.tag}}{{trimPrefix build.tag "v"}}-{{/if}}windows-amd64
+    image: plugins/npm:{{#if build.tag}}{{trimPrefix build.tag "v"}}-{{/if}}windows-1803
     platform:
       architecture: amd64
       os: windows
-      variant: 1809
+      version: 1803
+  -
+    image: plugins/npm:{{#if build.tag}}{{trimPrefix build.tag "v"}}-{{/if}}windows-1809
+    platform:
+      architecture: amd64
+      os: windows
+      version: 1809