Add ntfy.sh notification provider

[Avi0n]

Added ntfy.sh notication provider. All it needs is the ntfy topic. ntfy.sh docs for reference: https://docs.ntfy.sh/publish/

[ndrone]

Could this replace all the other notification types?

[Avi0n]

@ndrone Sorry, what do you mean by replace? Do you mean remove all other notification providers other than ntfy.sh? Or that my code has a problem?

[ndrone]

@ndrone Sorry, what do you mean by replace? Do you mean remove all other notification providers other than ntfy.sh? Or that my code has a problem?

yes replace all other notification providers.

[Avi0n]

Ah I see. I feel Slack and Discord would still be useful since they are much more popular platforms than ntfy.sh, but I will of course leave it up to the maintainer.

[K0p1-Git]

while I think its a good addition, slack and discord are still common. Hence, I don't think it should be removed.

[Avi0n]

That was my thought as well. This PR doesn't remove any notification providers, it just adds ntfy.

I realized ntfy also supports self-hosting the server, so I added support for custom URI's as well.