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/playtime/modules/ROOT/pages/usage.adoc

@@ -0,0 +1,19 @@
+= Basic usage
+
+Let's get familiar with the basics!
+
+A typical Playtime usage scenario, from beginning to end, looks like this:
+
+. xref:usage/prepare.adoc[]
+. xref:usage/create.adoc[]
+. xref:usage/play.adoc[]
+. xref:usage/grid-controllers.adoc[]
+. xref:usage/adjust.adoc[]
+. xref:usage/structure.adoc[]
+. xref:usage/arrangement.adoc[]
+. xref:usage/render.adoc[]
+
+In the following sections, we will learn step by step how to do this.
+
+TIP: This guide assumes that you already installed Playtime.
+If not, head to the xref:installation.adoc[] page!