style: add rustfmt.toml

.github/workflows/rust.yml

@@ -16,10 +16,8 @@ jobs:
   rustfmt:
     runs-on: ubuntu-latest
     steps:
-      - name: Setup Rust
+      - uses: dtolnay/rust-toolchain@nightly
-        uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: stable
           components: rustfmt
       - uses: actions/checkout@v4
       - run: cargo fmt --check --verbose

rustfmt.toml

@@ -0,0 +1,8 @@
+# https://github.com/rust-lang/rustfmt/blob/master/Configurations.md
+format_code_in_doc_comments = true
+format_macro_matchers = true
+group_imports = "StdExternalCrate"
+imports_granularity = "Module"
+normalize_doc_attributes = true
+reorder_impl_items = true
+use_field_init_shorthand = true