Modify rustfmt config file

Copy the current `rusntfmt` config file from `rust-bitcoin` and run the
formatter.

examples/point.rs

@@ -17,9 +17,7 @@ fn main() {
 
     println!();
     println!("Looking in map for key: {}", a);
-    let found = map
-        .get(Ordered::from_ref(&a))
-        .expect("failed to look up key");
+    let found = map.get(Ordered::from_ref(&a)).expect("failed to look up key");
     println!("Found it, with value: {}", found);
 }
 

rustfmt.toml

@@ -1,19 +1,24 @@
-max_width = 100
+ignore = []
 hard_tabs = false
 tab_spaces = 4
 newline_style = "Auto"
 indent_style = "Block"
-use_small_heuristics = "Default"
-fn_call_width = 80
-attr_fn_like_width = 70
-struct_lit_width = 80
-struct_variant_width = 35
-array_width = 60
-chain_width = 60
-single_line_if_else_max_width = 50
+
+max_width = 100 # This is number of characters.
+# `use_small_heuristics` is ignored if the granular width config values are explicitly set.
+use_small_heuristics = "Max"    # "Max" == All granular width settings same as `max_width`.
+# # Granular width configuration settings. These are percentages of `max_width`.
+# fn_call_width = 60
+# attr_fn_like_width = 70
+# struct_lit_width = 18
+# struct_variant_width = 35
+# array_width = 60
+# chain_width = 60
+# single_line_if_else_max_width = 50
+
 wrap_comments = false
 format_code_in_doc_comments = false
-comment_width = 80
+comment_width = 100             # Default 80
 normalize_comments = false
 normalize_doc_attributes = false
 format_strings = false
@@ -22,7 +27,7 @@ format_macro_bodies = true
 hex_literal_case = "Preserve"
 empty_item_single_line = true
 struct_lit_single_line = true
-fn_single_line = true
+fn_single_line = true           # Default false
 where_single_line = false
 imports_indent = "Block"
 imports_layout = "Mixed"
@@ -41,7 +46,7 @@ combine_control_expr = true
 overflow_delimited_expr = false
 struct_field_align_threshold = 0
 enum_discrim_align_threshold = 0
-match_arm_blocks = true
+match_arm_blocks = false        # Default true
 match_arm_leading_pipes = "Never"
 force_multiline_blocks = false
 fn_params_layout = "Tall"
@@ -52,8 +57,8 @@ trailing_comma = "Vertical"
 match_block_trailing_comma = false
 blank_lines_upper_bound = 1
 blank_lines_lower_bound = 0
-edition = "2018"
-version = "One"
+edition = "2021"
+style_edition = "2021"
 inline_attribute_width = 0
 format_generated_files = true
 merge_derives = true
@@ -65,9 +70,8 @@ color = "Auto"
 unstable_features = false
 disable_all_formatting = false
 skip_children = false
-hide_parse_errors = false
+show_parse_errors = true
 error_on_line_overflow = false
 error_on_unformatted = false
-ignore = []
 emit_mode = "Files"
 make_backup = false