Add ntfy support

[dhn]

This patch adds support for ntfy (ntfy.sh). For example:

• NTFY_HOST: The host (public instance: https://ntfy.sh) or a personal instance
• NTFY_TOPIC: The topic (channel) that was subscribed
• NTFY_TOKEN: Private token for a personal instance

$ python3 credmaster.py \
    --access_key ${ACCESS_KEY} \
    --secret_access_key ${SECRET_KEY} \
    --plugin ${PLUGIN} \
    -u ${USER_LIST} \
    -p ${PWD_LIST} \
    -a useragents.txt \
    -o ${OUTPUT_FILE} \
    --ntfy_host ${NTFY_HOST} \
    --ntfy_topic ${NTFY_TOPIC} \
    --ntfy_token ${NTFY_TOKEN} \
    --passwordsperdelay 3 -t 2 -j 10 -m 5 -d 120

[knavesec]

Thanks for the PR, looks great!