Add editorconfig [skip ci]

.editorconfig

+# editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 4
+trim_trailing_whitespace = true
+
+[*.md]
+trim_trailing_whitespace = false

.gitattributes

 # Ignore all test and documentation for archive
+/.editorconfig      export-ignore
 /.gitattributes     export-ignore
 /.gitignore         export-ignore
 /.scrutinizer.yml   export-ignore
 /.travis.yml        export-ignore
 /phpunit.xml.dist   export-ignore
 /tests              export-ignore
-/docs               export-ignore
+/docs               export-ignore
\ No newline at end of file