Send Base64 encoded image

Hello,

When I send a base64 encoded image to a topic, I get the following error in the plugin:

`logger=plugin.grafana-mqtt-datasource t=2024-07-22T17:04:36.467584207Z level=error msg="error parsing message" error="invalid value"`

Is it possible to send an image via MQTT using your plugin?

Best regards,

Nicolas