Vendor helgoboss/helgobox (ReaLearn) as basis for custom UI fork

Stripped upstream git history; starting point for replacing the native
SWELL/Win32 mapping UI with something more suited to bulk editing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

plugin-reaper-realearn/doc/realearn/modules/ROOT/pages/sources/virtual.adoc

@@ -0,0 +1,20 @@
+= Source "Virtual"
+
+See xref:further-concepts/source.adoc#virtual-source[].
+
+== Type menu
+
+See xref:further-concepts/compartment.adoc#virtual-control-element-type[].
+
+== ID section
+
+See xref:further-concepts/compartment.adoc#virtual-control-element-id[].
+
+=== Pick menu
+
+The convenient picker provides IDs from standardized xref:further-concepts/compartment.adoc#virtual-control-scheme[virtual control schemes].
+It also contains a category for accessing the virtual control elements that are currently exposed by the xref:key-concepts.adoc#controller-compartment[].
+
+=== ID field
+
+Lets you enter the ID manually.