As Visual Studio Code is the most popular editor at the moment, it makes
sense to recommend the EditorConfig extension because it's not included
by default. Also enable the final newline in files again as that was the
default until the EditorConfig file was added.
Add an EditorConfig file to ensure all editors know how to edit files
correctly. Apply conservative settings based on the existing files. Rust
options are based on the defaults of `rustfmt`.