Hubitat definitely does not support this natively. Amazon doesn't really either--there is no way to play arbitrary audio, at least not without writing a skill dedicated to that purpose like a radio station might (you know, the bad ones that don't use iHeartRadio or something I can actually play on multiple devices...).
The closest I can think of is Echo Speaks. This is a community app that can help manipulate some things on Echo devices. This is not supported by Hubitat or Amazon. It could break at any time if Amazon changes their mind about anything. It can't play an MP3 file per se, but it can play music from any Alexa-supported service.
If you don't insist on the Echo, there are other options: VLCThing (community), LANnouncer (community--only used it for TTS and I don't think it does music), and the native Sonos integration, and others may have more ideas.
