Provide clear sample configs for all environment permutations

[VTimofeenko]

This repo should have a set of sample configurations that cover the following scenarios:

1. Starting OS (NixOS/not NixOS)
2. Home-manager use (yes/no for NixOS, yes for "not NixOS" in 1.)
3. All features except for known not implemented configurations
4. Application-specific remaps

Every permutation should be as self-contained as possible without innovative and novel arguments passing -- just a flake.nix and maybe a testDriver package. Ideally the tests in ever-in-development #16 should cover as many of these scenarios as possible.

After this is done, README should be updated.

See #43, #38, #32, #30, #26