Add default button mapping to BUILD-ODBETA.md

BUILD-ODBETA.md

@@ -119,3 +119,53 @@ Now we build for this configuration:
 >     - `gmu.rg350.conf`, `gmuinput.rg350.conf` and `rg350.keymap` are the specific configurations used for anbernic devices.
 
 If all went well, an opk file will be generated in your gmu folder.
+
+## Button defaults
+
+The default button mapping is as follows:
+
+### Modifier
+Default Modifier is assigned to `L1` button
+
+### Global
+
+```
+R2           - Skip to next track in playlist/Start playback
+L2           - Skip to previous track in playlist
+Mod+R2       - Seek 10 seconds forward (**)
+Mod+L2       - Seek 10 seconds backward (**)
+X            - Pause/resume playback
+Mod+X        - Stop playback
+Mod+START    - Exit player
+Mod+SELECT   - Lock/Unlock buttons amd screen off/on
+START        - Toggle file browser/playlist view/track info
+LEFT/RIGHT   - Increase/lower volume
+Mod+A        - Program info
+Mod+LEFT     - Toggle time elapsed/remaining
+```
+
+### File browser
+
+```
+A            - Play file without adding it to the playlist
+B            - Add selected file to the playlist/Change directory
+Y            - Add selected directory and all sub directories
+Mod+B        - Insert selected file after selected playlist item
+```
+
+### Playlist
+
+```
+A            - Change play mode (continue, repeat all, 
+               repeat track, random, random+repeat)
+B            - Play selected track
+Y            - Remove selected track
+Mod+Y        - Clear playlist
+Mod+RIGHT    - Enqueue selected item
+
+Track info viewer:
+A            - Show/hide cover artwork
+B            - Show/hide text
+```
+
+(**) Seeking does not work with all file formats.