Not that many packages get included with Linux Mint directly, as you can see if you browse http://packages.linuxmint.com/list.php?release=Qiana
. That's mostly Cinnamon, MATE, and the Mint tools. The rest comes from Ubuntu or Debian package bases.
As you've not linked to your public source code repository (all Linux Mint developed software is open source, licensed under the GPL, with public source code repository on GitHub), what does your program do? How does it compare with the various text to speech programs available on Linux Mint? For example compared to Orca Screen Reader (the default text to speech program for vision impaired users).
Get in contact with the Mint developers on IRC #linuxmint-dev if you want to contribute software, though be ready to answer the question I raised (what sets it apart from already included TTS programs
BTW, using the "Mint" name will confuse users into thinking it was developed and tested by Linux Mint and is officially supported by them. That's not the case. So unless you get your program adopted as an official Mint program, I'd suggest using a different name to avoid confusing users so (and getting into trademark dispute with the Mint developers).
I suggest you start with a PPA for your program. You can do so through Launchpad; Canonical's free build service. That's used by many developers to make their software available for users of Ubuntu and derivative distros like Linux Mint. Get started: https://help.launchpad.net/Packaging/PPA
. PPAs are easily used by Linux Mint users, through Mint's Software Sources program, allowing them to easily install your program from there (and get updates when you publish a new version). As already mentioned, don't confuse users about your program being official Linux Mint software by calling it "Mint".
Your question raises a lot of questions in return
Not meaning to sound discouraging.