editorconfig configuration files hold editor style hints, and
is supported by many popular editors. See https://editorconfig.org/ .
The vast majority of the mpv source/text files are already styled as
4 space indentation, trailing newline at EOF, and UTF-8 encoding.
This commit adds a single .editorconfig root file which applies these
rules to all files using the glob "[*]".
If it turns out to be too inclusive then we can narrow it down later.
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
