Update CHANGELOG.md

CHANGELOG.md

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 ## 0.2.0 (WIP)
 
+### Comprehensive Changes
+
 - Many functions are asynchronous
-  - To make create an `async` main function you can use the attribute `#[libtock::main]`
+  - To create an `async` main function you can use the attribute `#[libtock::main]`
   - To retrieve the value of an asynchronous `value`, use `value.await`
   - This is only possible within an `async fn`, so either
     - Make the caller `fn` of `.await` an `async fn`
     - Not recommended: Use `core::executor::block_on(value)` to retrieve the `value`
+- Most API functions, including `main()`, return a `Result<T, TockError>`
+- All drivers can exclusively be retrieved by `retrieve_drivers` which returns a `Drivers` singleton. Drivers can be shared between different tasks only if it is safe to do so.
+
+### Changed APIs
+
+- The basic APIs have been made consistent. They are initialized via driver factories and no longer require a `WithCallback` object, s.t. the callback subscription is more intuitive. The affected APIs are:
+  - LEDs
+  - Buttons
+  - GPIO
+  - Temperature
+- The timer API now supports concurrent sleep operations
+
+### Syscalls
+
+- `syscalls::subscribe` is actually usable
 - `syscalls::yieldk_for` is no longer available
   - Yielding manually is discouraged as it conflicts with Rust's safety guarantees. If you need to wait for a condition, use `futures::wait_until` and `.await`.
 - `syscalls::yieldk` has become `unsafe` for the same reason
-- Commands are no longer `unsafe`
+- `syscalls::command` is no longer `unsafe`
 - The low-level syscalls have been moved to `syscalls::raw`
   - `syscalls::subscribe_ptr` becomes `syscalls::raw::subscribe`
   - `syscalls::allow_ptr` becomes `syscalls::raw::allow`
+
+### Miscellaneous
+
 - Targets without support for atomics can be built
-- Most API functions, including `main()`, return a `Result<T, TockError>`
-- The library now supports parallel timers
-- all drivers can exclusively be retrieved by `retrieve_drivers` which returns a `Drivers`-singleton. Drivers can be shared between different tasks only if it is safe to do so.
 
 ## a8bb4fa9be504517d5533511fd8e607ea61f1750 (0.1.0)