Fix Windows shortcut updates and sign .node artifacts

- use `replace` when writing Windows mpv shortcuts and update tests
- include `*.node` files in SignPath Authenticode signing config
- document WinShell plugin sourcing in installer/build notes

build/signpath-windows-artifact-config.xml

@@ -12,6 +12,9 @@
         <pe-file path="*.dll" max-matches="unbounded">
           <authenticode-sign />
         </pe-file>
+        <pe-file path="*.node" max-matches="unbounded">
+          <authenticode-sign />
+        </pe-file>
       </directory>
     </zip-file>
   </zip-file>