.editorconfig?

[chantastic]

This StackOverflow answer suggests that GitHub honors .editorconfig.

I no longer use the plugin but it could be the answer to expressed concerns about the 8-space tab default when viewing source online.

something like this would probably cover us for now.

root = true

[*]
end_of_line = lf
insert_final_newline = true

# Matches multiple files with brace expansion notation
[*.{js,html,css}]
charset = utf-8
indent_style = tab
indent_size = 4
trim_trailing_whitespace = true

[*.md]
trim_trailing_whitespace = false