feat: make keybindings configurable

src/ruby_host.rb

@@ -31,12 +31,13 @@ module Vamp
       nil
     end
 
-    def bind(key, command)
+    def bind(key, command, mode: "normal")
       key = Vamp.string!(key, "binding key")
-      command = Vamp.string!(command, "binding command")
-      raise ArgumentError, "binding key must be one character" unless key.length == 1
-      raise ArgumentError, "binding command must not be empty" if command.empty?
-      @bindings << { "key" => key, "command" => command }
+      mode = Vamp.string!(mode, "binding mode")
+      command = Vamp.string!(command, "binding command") unless command.nil?
+      raise ArgumentError, "binding key must not be empty" if key.empty?
+      raise ArgumentError, "binding command must not be empty" if command == ""
+      @bindings << { "mode" => mode, "key" => key, "command" => command }
       nil
     end