Editor Config (4 spaces, *nix line endings)

.editorconfig

# http://editorconfig.org
#
# An .editorconfig file describes minor formatting tweaks
#   to apply to text files to ensure consistent formatting
#   in a project with multiple developers.
#
# Plugins exist to allow editors / IDEs to automatically apply
#   these tweaks to a project when an .editorconfig file is
#   found in the project's root directory.
#
# Plugins
#   Sublime - https://packagecontrol.io/packages/EditorConfig
#   IntelliJ - https://plugins.jetbrains.com/plugin/7294
#   (most other IDEs/Editors - Google it)
root = true

[*]
indent_style = space
indent_size = 4
end_of_line = lf
charset = utf-8
trim_trailing_whitespace = true
insert_final_newline = true

[*.md]
# for empty lines in code blocks with 4 space indentation (some MD editors don't like ``` blocks ```)
trim_trailing_whitespace = false

[package.json, config.json, .babelrc, npm-shrinkwrap.json]
# tools for these files normalize their JSON output with 2 spaces per level
indent_size = 2