Documentation on using PM2

[GuyHarwood]

The old documentation on how to configure PM2 with Linux App Service no longer exists on Github and references to PM2 have recently been removed from the official Linux App Service documentation (but still appear in Googles cache).

Can you at least add a readme to this repository on how to set that up from the docker blade under Linux App Service in the azure portal.

Also information on how to debug failed startup, and expected format for the 'start up file' input field in the portal blade.

I appreciate we can infer what to enter, but it should be made obvious. For example, entering pm2 start pm2.json causes a failed start, but works fine without PM2, and the pm2.json works fine locally. Clarity either way on whether this feature is still supported (which in theory, it appears to be) would be helpful.