Add CHANGELOG.md, and append 0.4.0 release notes

Author: tankyleo

CHANGELOG.md

@@ -0,0 +1,18 @@
+# 0.4.0 - Nov 11, 2025
+
+## Crate Metadata
+- Rename `vss-client` crate to `vss-client-ng` (#46).
+- Move repository from <https://github.com/lightningdevkit/rust-vss-client> to <https://github.com/lightningdevkit/vss-client> (#48).
+
+## Features and API updates
+- Bump MSRV to 1.75.0 (#38).
+- Add `VssClient::from_client_and_headers` constructor (#39).
+- Allow to set `aad` in `StorableBuilder::{build, deconstruct}` (#40).
+- Pass the `data_encryption_key` by reference to `StorableBuilder::{build, deconstruct}` (#40).
+
+## Bug Fixes and Improvements
+- Set a 10 second timeout on all HTTP client requests (#39).
+
+In total, this release features 15 files changed, 205 insertions, 1162 deletions in 19 commits from 2 authors in alphabetical order:
+- Elias Rohrer
+- Leo Nash