reg: add page (#1908)

pages/windows/reg.md

@@ -0,0 +1,16 @@
+# reg
+
+> A command line interface for managing keys and their values in the Windows registry.
+> See `reg-query`, `reg-add` and other pages for additional information.
+
+- Execute registry commands:
+
+`reg {{command}}`
+
+- Display general information and list all available commands:
+
+`reg /?`
+
+- Call help on a specific command:
+
+`reg {{command}} /?`