doc: update CHANGELOG with new reserve mode constants (#188)

and a couple minor enhancements

CHANGELOG.md

@@ -8,13 +8,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
-
-- `log2` and `log` math functions in stdlib: PR [#166](https://github.com/tact-lang/tact/pull/166)
+- `log2` and `log` math functions in `@stdlib/math`: PR [#166](https://github.com/tact-lang/tact/pull/166)
+- Reserve mode constants in `@stdlib/reserve`, namely `ReserveExact`, `ReserveAllExcept`, `ReserveAtMost`, `ReserveAddOriginalBalance`, `ReserveInvertSign`, `ReserveBounceIfActionFail`: PR [#173](https://github.com/tact-lang/tact/pull/173)
 
 ### Changed
 - Update the `dump` function to handle addresses: PR [#175](https://github.com/tact-lang/tact/pull/175)
-
-- The implicit empty init function is now present by default in the contract if not declared
+- The implicit empty `init` function is now present by default in the contract if not declared: PR [#167](https://github.com/tact-lang/tact/pull/167)
 
 ### Fixed