docs: Add CMake build type release note snippet

docs/markdown/snippets/cmake_build_type.md

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+## Meson now propagates its build type to CMake
+
+When the CMake build type variable, `CMAKE_BUILD_TYPE`, is not set via the
+`add_cmake_defines` method of the [`cmake options` object](CMake-module.md#cmake-options-object),
+it is inferred from the [Meson build type](Builtin-options.md#details-for-buildtype).
+Build types of the two build systems do not match perfectly. The mapping from
+Meson build type to CMake build type is as follows:
+
+- `debug` -> `Debug`
+- `debugoptimized` -> `RelWithDebInfo`
+- `release` -> `Release`
+- `minsize` -> `MinSizeRel`
+
+No CMake build type is set for the `plain` Meson build type. The inferred CMake
+build type overrides any `CMAKE_BUILD_TYPE` environment variable.