How to set per-project ripgrep and fzf exclude rules

In some projects, you want ripgrep to ignore some files that aren’t in .gitignore — things like statically generated files in a Hugo site (like this one). You can do this by adding them to a local .ignore file.

This also works for fzf.

This ensures Vim’s :grep and :Files (via fzf.vim) commands don’t find irrelevant files.