Add editorconfig config file

See https://editorconfig.org/ for details.

(neo)vim: https://github.com/editorconfig/editorconfig-vim
emacs:    https://github.com/editorconfig/editorconfig-emacs

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

.editorconfig

@@ -0,0 +1,18 @@
+root = true
+
+[*]
+charset = utf-8
+max_line_length = 80
+end_of_line = lf
+trim_trailing_whitespace = true
+insert_final_newline = false
+
+[*.{c,h}]
+indent_style = space
+indent_size = 4
+tab_width = 4
+
+[{CMakeLists.txt,*.cmake}]
+indent_style = space
+indent_size = 4
+tab_width = 4