Always send mqtt message, but snapshot only if enabled & configured

[numericOverflow]

Previously if snapshot was enabled, mqtt_message was not sent to mqtt_topic.

Now, it always pubs to the mqtt_topic, but optionally and additionally pubs to the mqtt_snap_topic.

This change allows for monitoring subs that don't want snap, they can monitor the text-only pubs. For example, I log the motion triggers via text string, but don't need to get the snapshots for logging on all devices, they are already in frigate/NVR/etc. It generally makes automation triggers easier having the option of snaphot or message text available and then just subscribing to the appropriate topic

mqtt_message & mqtt_topic were already required parameters to the script so I wouldn't expect this to be a breaking change for anything. It shouldn't be much additional overhead, assuming mqtt_message configured is reasonable. Since they are already choosing to send a snapshot image, sending the message text as well should be negligible.

[spamcop]

script should allow to set mqtt_snap_topic via some parameter

[numericOverflow]

Hey @gtxaspec or @themactep - any reason this PR can't be merged for better MQTT flexibility?