support passing markdown in ntfy notifications

[applesoff]

Description

With the command curl -H "Markdown: yes" you can set ntfy to display with markdown formatting making notifications better.

Please consider adding this as an option in diun for rich text notifications.

[crazy-max]

-H "Markdown: yes"

Do you have link to the documentation about it please?

[applesoff]

https://docs.ntfy.sh/publish/?h=markdown#markdown-formatting
I don't know if changing anything is needed. I thought there was going to be an addition of markdown to the title but it looks like they do not have interest in adding this per binwiederhier/ntfy#889 (comment)

Though if a clickable link could be added I would also like this. I can open another issue though. https://docs.ntfy.sh/publish/?h=click#click-action