Change package.json indent size to 2

Due to the change presented in de383ba, we will now use the
npm version tool to modify our version property automatically.
Because npm doesn't respect the current indentation of the
package.json file, we have to follow their rules and indent with 2 spaces
as well.

Author: Gustavo Henke

.editorconfig

@@ -8,7 +8,8 @@ end_of_line = lf
 charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
-
-[*]
 indent_style = space
-indent_size = 4
+indent_size = 4
+
+[package.json]
+indent_size = 2