Add an option to skip certain filetypes.

[yyk]

For example, markdown's trailing spaces has special meanings.

[GNOMES]

If this gets approved, I think there should be an update to the repo's README.md file with config that can be used in a dedicated config file that can be sourced by init.lua

If someone wanted to do multiple exclusions, it can be messy to add these to the Packer Use Lua (in the way the included example does).