Add .editorconfig. (geonetwork#1517)

Author: François Prunayre

.editorconfig

@@ -0,0 +1,14 @@
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.java]
+indent_size = 4
+
+[*.md]
+indent_size = 2
+trim_trailing_whitespace = false