feat: parse into a Document that keeps order and comments

Assisted-by: DeepSeek V4.1 Flash

README.md

@@ -23,6 +23,9 @@ the entire official [toml-test](https://github.com/toml-lang/toml-test) suite:
   user types with text methods need no configuration.
 - **Cancellation**: every entry point has a `*Context` sibling that honours a
   `context.Context`.
+- **Ordered documents**: `Parse` gives a `*Document` that keeps the key order,
+tells an inline table from a header one, and carries the comments; `ParseMap`
+gives the plain `map[string]any` tree.
 - **Configurable emission**: `Encoder` options for declaration-order output,
   omitting empty arrays, literal multiline strings, and inlining small
   sub-tables.
@@ -67,8 +70,9 @@ err := interpres.Unmarshal(data, &cfg)
 ```
 
 Fields match by the `toml:"name"` tag, or by the lower-cased field name when no
-tag is present; `toml:"-"` skips a field. `Parse` returns the untyped
-`map[string]any` tree instead, and `UnmarshalContext` accepts a context.
+tag is present; `toml:"-"` skips a field. `Parse` returns a `*Document` that
+also carries the key order and the comments, `ParseMap` returns the plain
+`map[string]any` tree, and `UnmarshalContext` accepts a context.
 
 ### Encode from a struct