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/main/lib/helgoboss-learn/Cargo.toml

@@ -0,0 +1,43 @@
+[package]
+name = "helgoboss-learn"
+version = "0.1.0"
+authors = ["Benjamin Klum <benjamin.klum@helgoboss.org>"]
+edition = "2021"
+publish = false
+
+[dependencies]
+base.workspace = true
+helgoboss-midi.workspace = true
+tracing.workspace = true
+num.workspace = true
+num_enum.workspace = true
+approx.workspace = true
+derive_more.workspace = true
+serde.workspace = true
+serde_repr.workspace = true
+# For being able to (de)serialize using FromStr
+serde_with.workspace = true
+lazycell.workspace = true
+# For being able to exclude some fields from the hash function (necessary for ignoring already learned sources)
+derivative.workspace = true
+# For OSC
+rosc.workspace = true
+# For using the Bpm type
+reaper-common-types.workspace = true
+# For letting the here defined raw MIDI data structure implement the REAPER MIDI event type
+reaper-low = { workspace = true, optional = true }
+# For RgbColor type conversion
+image = { workspace = true, default-features = false }
+# For tokenizing sys-ex patterns
+logos.workspace = true
+# For easy error types
+thiserror.workspace = true
+partial-min-max = "0.4.0"
+nom.workspace = true
+regex.workspace = true
+once_cell.workspace = true
+# For convenient converting of OSC feedback arg prop to enum variant and back
+strum.workspace = true
+serde_json.workspace = true
+# For making consumers being able to use some newtypes as atomics
+bytemuck = { workspace = true, features = ["derive"] }