Add .editorconfig

[ftzi]

E.g.

# EditorConfig helps developers define and maintain consistent
# coding styles between different editors and IDEs
# editorconfig.org

root = true

[*]

# change these settings to your own preference
indent_style = space
indent_size = 2

# we recommend you to keep these unchanged
end_of_line = lf
charset = utf-8
trim_trailing_whitespace = true
insert_final_newline = true

[*.md]
trim_trailing_whitespace = false

(https://github.com/callstack/react-native-paper/blob/main/.editorconfig).

Read other projects' .editorconfig to make the best one.