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/midi/midi-script.adoc

@@ -0,0 +1,23 @@
+= Source "MIDI Script"
+
+[[source-midi-script]]
+This source is feedback-only and exists for enabling more complex feedback use cases such as controlling LCDs that are not yet supported by the xref:sources/midi/display.adoc[].
+It lets you write an EEL or Luau script that will be executed whenever ReaLearn "feels" like it needs to send some feedback to the MIDI device.
+
+== Kind menu
+
+Whether to use the EEL or Luau language.
+
+== Script field
+
+The script.
+Is disabled if the script contains more than one line.
+
+See xref:further-concepts/source.adoc#midi-source-script[] for details.
+
+== More button (…)
+
+Opens the script in a separate window (for multi-line scripts).
+
+TIP: Prefer the xref:sources/midi/display.adoc[] over this one whenever possible.
+It's easier to use.