Add editorconfig configuration (#7761)

Most editors support editorconfig or have plugins for it, its universal
config for specifying whitespace/line-length rules. Especially useful for
editors like Neovim who support it out of the box and dont have other concepts
of per project whitespace configuration.

https://editorconfig.org/

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

.editorconfig

@@ -0,0 +1,4 @@
+[*.lua]
+trim_trailing_whitespace = false
+indent_style = tab
+max_line_length = 120