WRS-1346 - Specify schema in build-script and rename "product=" attributes to "instance=" attributes

Author: lananovikova10

docs/StardustDocs/cfg/build-script.xml

@@ -1,10 +1,10 @@
-<?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE root
-        SYSTEM "https://resources.jetbrains.com/stardust/build-script.dtd">
+    SYSTEM "https://helpserver.labs.jb.gg/help/schemas/mvp/build-script.dtd">
+
 <root>
     <builds>
-        <product id="d" master="project.ihp" family="idea">
+        <instance id="d" master="project.ihp" family="idea">
             <artifact type="web2" name="webHelpD2.zip" platform="primary" local-update="true"/>
-        </product>
+        </instance>
     </builds>
 </root>