[Feature Request] Terminal emulator utility extension

Some community mod loaders for steam games use an environment provided terminal emulator as an interactive console and/or log (for example SMAPI for Stardew Valley) which the Steam Flatpak doesn't provide.
As completely sensible as that is it also would be nice to have a utility extension that made a terminal emulator available in the sandbox for those who need it. I made a personal locally built and installed extension that adds Alacritty so i can use it with SMAPI but i figured it might make sense to publish a version of that or something similar so others with the same issue can also benefit from it and i figured the best place to start on that would be here.

The issue names no files, tests, or entry points. Start by examining the repository's Steam Flatpak packaging and the locally built Alacritty extension described in the report, then define how a published terminal utility should be exposed for SMAPI; done means an installable extension provides the requested terminal in the sandbox.

Written by the indexing model from the issue text.