feat: add fmt file with some options

Author: SergioRibera

rustfmt.toml

@@ -0,0 +1,9 @@
+max_width = 100
+hard_tabs = false
+tab_spaces = 4
+newline_style = "Auto"
+reorder_imports = true
+reorder_modules = true
+remove_nested_parens = true
+merge_derives = true
+imports_granularity = "Crate"