Take Mac into account in keyboard shortcuts

Signed-off-by: Paul Tötterman <paul.totterman@iki.fi>

docs/shortcuts.md

@@ -1,9 +1,11 @@
 # Keyboard Shortcuts
 
-- <kbd>Ctrl</kbd>+<kbd>m</kbd> - toggle markdown
-- <kbd>Ctrl</kbd>+<kbd>d</kbd> - toggle mic mute
-- <kbd>Ctrl</kbd>+<kbd>e</kbd> - toggle video on/off
-- <kbd>Ctrl</kbd>+<kbd>k</kbd> - jump to named room
+The modifier is <kbd>Ctrl</kbd> on Windows & Linux and <kbd>⌘</kbd> on Mac.
+
+- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>m</kbd> - toggle markdown
+- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>d</kbd> - toggle mic mute
+- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>e</kbd> - toggle video on/off
+- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>k</kbd> - jump to named room
 - <kbd>↑</kbd>/<kbd>↓</kbd> - navigate within room list
 - <kbd>PageUp</kbd>/<kbd>PageDown</kbd> - scroll timeline up/down
-- <kbd>Ctrl</kbd>+<kbd>Home</kbd>/<kbd>End</kbd> - jump to timeline start/end
+- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>Home</kbd>/<kbd>End</kbd> - jump to timeline start/end