Add support for setting vendor/device IDs (#10)

Sets vendor and product IDs, defaults to the prior default values.
This is needed for some games to be able to correctly identify the virtual devices since not all games support device indexes.

Reviewed-on: https://codeberg.org/annabunches/joyful/pulls/10

internal/configparser/schema.go

@@ -11,6 +11,8 @@ type Config struct {
 // TODO: configure custom unmarshaling so we can overload Buttons, Axes, and RelativeAxes...
 type DeviceConfigVirtual struct {
 	Name            string
+	VendorId				string `yaml:"vendor_id,omitempty"`
+	DeviceId				string `yaml:"device_id,omitempty"`
 	Preset          string
 	NumButtons      int `yaml:"num_buttons,omitempty"`
 	NumAxes         int `yaml:"num_axes,omitempty"`