docs: 2.2 release updated with mag_ratio

docs/blog/posts/2.2.0-released.md

@@ -372,3 +372,28 @@ inside of the `mp_units::si` subnamespace and not in `mp_units::isq` like it was
 (**breaking change**).
 
 Also, the header itself was split into smaller pieces that improve C++20 modules definitions.
+
+
+## `ratio` made an implementation detail of the library
+
+We decided not to expose `ratio` and associated types in the public interface of the library
+(**breaking change**). Standardization of it could be problematic as we have
+[`std::ratio`](https://en.cppreference.com/w/cpp/numeric/ratio/ratio) already.
+
+Alternatively, we introduced a new helper called `mag_ratio` to provide the magnitude of the unit
+defined in terms of a rational conversion factor. Here is a comparison of the code with previous
+and current definitions:
+
+=== "Now"
+
+    ```cpp
+    inline constexpr struct yard : named_unit<"yd", mag_ratio<9'144, 10'000> * si::metre> {} yard;
+    inline constexpr struct foot : named_unit<"ft", mag_ratio<1, 3> * yard> {} foot;
+    ```
+
+=== "Before"
+
+    ```cpp
+    inline constexpr struct yard : named_unit<"yd", mag<ratio{9'144, 10'000}> * si::metre> {} yard;
+    inline constexpr struct foot : named_unit<"ft", mag<ratio{1, 3}> * yard> {} foot;
+    ```