That sounds like it would probably be a SMAPI mod, which is a mod written in C# (programming) rather than content packs made up of assets and text files for an existing framework. If you're already familiar with C# or a similar language, it doesn't sound difficult, but if not, there's
a learning process.
That page has step-by-step instructions, with pictures, for how to set up your first project in Visual Studio and create a tutorial mod. The FAQ at the bottom also has information on how to decompile the game, and links to the very well-documented SMAPI APIs.
It doesn't teach you C#. In addition to the many tutorials and classes available on the internet, most SMAPI mods made for Stardew Valley are open source, so you can go see how someone else did something similar and learn from their work. The
compatibility page has a "show advanced info" checkbox that, when checked, will link the source code for every open-source mod.
I'm not an expert, but it doesn't sound like the basic idea would be too hard to make. My guess would be you'd either check for eaten food on right-click to add in your message, or patch the game code somewhere for eating (*gestures vaguely* I am not looking at a decompile and don't know what that looks like off the top of my head, so I am guessing :P ). How you organized the messages themselves and decided which message to use depends on what you wanted (unique messages for every item? predetermined groups of items? context-tag dependent?) but you can figure that out once there is a message, hehe.
If you've never modded anything before and are not familiar with programming at all, be patient with yourself and consider making some basic content mods to get familiar with how the game uses files while learning just enough C# to get going. You definitely don't need to be a pro.