documentation: document editor-usage

Add a very basic overview of the editor-usage, and a list of keyboard
shortcuts.

README

@@ -28,6 +28,38 @@ Once the prerequisites are installed, the example can be compiled much like
 the editor; by opening examples.sln and selecting "Build" -> "Build Solution"
 from the menu.
 
+Using the editor
+----------------
+The GNU Rocket editor is laid out like a music-tracker; tracks (or columns)
+and rows. Each track represents a separate "variable" in the demo, over the
+entire time-domain of the demo. Each row represents a specific point in time.
+Each row consists of a set of key-frames, which are interpolated over time
+according to their interpolation modes.
+
+Keyboard shortcuts
+-------------------
+Some of the GNU Rocket editor's features are available through the menu and
+some keyboard shortcut. Here's a list of the supported keyboard shortcuts:
+
+Up/Down/Left/Right        Move cursor
+PgUp/PgDn                 Move cursor 16 rows up/down
+Home/End                  Move cursor to begining/end
+Ctrl+Left/Right           Move track
+Enter                     Enter key-frame value
+Del                       Delete key-frame
+i                         Enumerate interpolation mode
+Space                     Pause/Resume demo
+Shift+Up/Down/Left/Right  Select
+Ctrl+C                    Copy
+Ctrl+V                    Paste
+Ctrl+Z                    Undo
+Shift+Ctrl+Z              Redo
+Ctrl+B                    Bias keyframes
+Shift+Ctrl+Up/Down        Quick-bias by +/- 0.1
+Ctrl+Up/Down              Quick-bias by +/- 1
+Ctrl+PgUp/PgDn            Quick-bias by +/- 10
+Shift+Ctrl+PgUp/PgDn      Quick-bias by +/- 100
+
 Bugs and feed-back
 ------------------
 Please report bugs or other feed-back to the GNU Rocket mailing list: