feat: Add TOML marshalling API

CHANGELOG.md

@@ -5,6 +5,43 @@ All notable changes to **interpres** are documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.1.0] — 2026-06-26
+
+Adds TOML emission to the previously read-only library, completing the
+`encoding/json`-style API.
+
+### Added
+
+**Marshalling**
+
+- `Marshal(v any) ([]byte, error)` — encode a struct or `map[string]V` value
+  to a TOML 1.0 document.
+- `Encoder` and `NewEncoder`, mirroring the `Decoder` shape for symmetry with
+  `Unmarshal`.
+- `Marshaler` interface (`MarshalTOML() (any, error)`) for types that need a
+  custom TOML shape; the returned value is encoded normally.
+- Struct fields are matched by `toml:"name"` tag (case-insensitive fallback to
+  field name; `toml:"-"` skips). Anonymous (embedded) fields without a tag
+  are inlined.
+- Slices and arrays of structs or maps become `[[a]]` arrays of tables; other
+  slices and arrays become TOML arrays. Empty or nil arrays of tables are
+  omitted; empty arrays of scalars emit as `key = []`.
+- Scalars encode as bool, int64, float64, string, `time.Time` (offset
+  date-time), `LocalDateTime`, `LocalDate`, or `LocalTime`.
+- `time.Time`, `LocalDateTime`, `LocalDate`, and `LocalTime` now have
+  `String()` methods that return their TOML-canonical rendering
+  (zero-padded to nanosecond precision when a fractional second is present).
+
+**Encoding policy**
+
+The emitter groups fields at every TOML level: scalars first, then
+sub-tables, then arrays of tables. Within each group the order matches struct
+field declaration order, or sorted key order for maps. The output is
+guaranteed to re-parse to an equivalent value tree via `Parse`, but is not
+byte-identical to any input that produced the value — comments, whitespace,
+map key order, and basic-vs-literal string quoting are not preserved. See
+the "Encoding" section of the README for the full set of rules.
+
 ## [1.0.0] — 2026-06-20
 
 First stable release: a dependency-free TOML 1.0 parser for Go that uses only