chore: document rustfmt options (#2055)

rustfmt.toml

@@ -1,12 +1,23 @@
-# configuration for https://rust-lang.github.io/rustfmt/
+# Configuration for https://rust-lang.github.io/rustfmt/
+edition = "2024"
 
+# E.g. Foo { a, b, c }
 use_field_init_shorthand = true
 
-# unstable options
+# Unstable options. These require a nightly compiler to use (cargo +nightly fmt).
+
+# We choose a wider comment width, as this tends to make comments more readable than truncating at
+# 80 characters.
+wrap_comments = true
 comment_width = 100
 format_code_in_doc_comments = true
-format_macro_matchers = true
+
+# `#[doc = "..."]` -> `/// ...`
+normalize_doc_attributes = true
+
+# We choose module granularity for imports as this tends to have the best balance between low
+# linecount while making it simple to understand diffs
 group_imports = "StdExternalCrate"
 imports_granularity = "Module"
-normalize_doc_attributes = true
-wrap_comments = true
+
+format_macro_matchers = true