Add .editorconfig for consistent coding styles

extensions/lang-english/.editorconfig

@@ -0,0 +1,17 @@
+# http://editorconfig.org/
+
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.{json,php}]
+indent_size = 4
+
+[*.md]
+trim_trailing_whitespace = false