* add `performance.byteCompileLua.enable` toggle to enable or disable
all byte compiling features
* add `performance.byteCompileLua.initLua` toggle to enable or
disable byte compiling of init.lua
* add `writeByteCompiledLua` helper for saving byte compiled lua source
code to the nix store
* `nixvim-print-init` utility is always pointed to uncompiled init.lua
* add tests
plenary.nvim is often pulled as a dependency of other plugins.
It has filetype definitions in `data/plenary/filetypes` directory.
Even though I don't think there are plugins using it instead of
vim.filetype, but it should be no harm to add this directory by default.
