A website to upload my ios app that anyone can download
Sorry, no...
The only (legitimate) way to do this is via the Apple App Store.
There may be a way to do this for jailbroken devices but that would be off-topic (I believe) for AskDifferent.
Yes.
AltStore exists, and uses completely legitimate methods, as Apple allows normal users to sign apps for their own personal devices, with one caveat: it needs to re-sign apps every 7 days (through USB or LAN connection to a PC with a Windows/Linux server installed).
It is completely open source, licensed under the AGPLv3: https://github.com/rileytestut/AltStore