Update changelog

Author: PicoJr

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [1.2.1](https://crates.io/crates/rtw/1.2.1) Jun 07, 2020
 
+* Add warning: CLI usage stable but not `lib.rs` content.
 * Fix doc.rs build issue (restore `lib.rs`).
 
 ## [1.2.0](https://crates.io/crates/rtw/1.2.0) Jun 07, 2020

README.md

@@ -11,6 +11,8 @@
 
 Command-line interface (CLI) time tracker.
 
+CLI usage is stable, underlying API is **not stable**.
+
 This project is heavily inspired from [Timewarrior](https://github.com/GothenburgBitFactory/timewarrior).
 
 > For a stable feature-rich CLI time tracker, please use Timewarrior: https://timewarrior.net/.

src/lib.rs

@@ -2,6 +2,8 @@
 //!
 //! Command-line interface (CLI) time tracker.
 //!
+//! CLI usage is stable, underlying API is **not stable**.
+//!
 //! This project is heavily inspired from [Timewarrior](https://github.com/GothenburgBitFactory/timewarrior).
 //!
 //! For a stable feature-rich CLI time tracker, please use Timewarrior: <https://timewarrior.net/>.