docs: backfill 0.1.0 changelog entry

CHANGELOG.md

@@ -12,3 +12,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - `fpk_writer_add_dir()` for library-level recursive directory packing.
+
+## [0.1.0] - 2026-09-15
+
+### Added
+
+- `FPK1` archive format: flat header/data-blobs/string-table/directory layout,
+  fixed little-endian on disk.
+- Reader API: `fpk_open`/`fpk_close`/`fpk_find`/`fpk_read`/`fpk_entry_count`/
+  `fpk_entry_at`.
+- Writer API: `fpk_writer_open`/`fpk_writer_add`/`fpk_writer_finalize`/
+  `fpk_writer_close`.
+- `fpack`/`funpack` CLI tools with full flag sets (`-o`/`-p`/`-q`/`-v`/`-h` and
+  `-d`/`-l`/`-p`/`-q`/`-v`/`-h` respectively).
+- Graceful Ctrl+C handling in `fpack`, cleaning up partial output.
+- Elapsed-time reporting on `fpack`/`funpack` completion.
+- Wide-char Windows filename support in `funpack`.
+- 64-bit seek/tell throughout, avoiding 32-bit truncation on large archives.