CMake: Change README-cmake to README-cmake.md with formatting.

Per @ClausKlein suggestion.

Author: Vollstrecker

README-cmake.md

@@ -0,0 +1,83 @@
+# For building with cmake at least version 3.12 (minizip 3.12) is needed
+
+In most cases the usual
+
+    cmake -S . -B build -D CMAKE_BUILD_TYPE=Release
+
+will create everything you need, however if you want something off default you can adjust several options fit your needs.
+Every option is list below (excluding the cmake-standard options), they can be set via cmake-gui or on cmdline with
+
+    -D<option>=ON/OFF
+
+## ZLIB-options with defaults ##
+
+    ZLIB_BUILD_TESTING=ON -- Enable Zlib Examples as tests
+
+    ZLIB_BUILD_SHARED=ON -- Enable building zlib shared library
+
+    ZLIB_BUILD_STATIC=ON -- Enable building zlib static library
+
+    ZLIB_BUILD_MINIZIP=ON -- Enable building libminizip contrib library
+
+If this option is turned on, additional options are available from minizip (see below)
+
+    ZLIB_INSTALL=ON -- Enable installation of zlib
+
+    ZLIB_PREFIX=OFF -- prefix for all types and library functions, see zconf.h.in
+
+    ZLIB_INSTALL_COMPAT_DLL=ON -- Install a copy as zlib1.dll
+
+This option is only on windows available and may/will be turned off and removed somewhen in the future.
+If you rely cmake for finding and using zlib, this can be turned off, as `zlib1.dll` will never be used.
+
+## minizip-options with defaults ##
+
+    MINIZIP_BUILD_SHARED=ON -- Enable building minizip shared library
+
+    MINIZIP_BUILD_STATIC=ON -- Enable building minizip static library
+
+    MINIZIP_BUILD_TESTING=ON -- Enable testing of minizip
+
+    MINIZIP_ENABLE_BZIP2=ON -- Build minizip withj bzip2 support
+
+A usable installation of bzip2 is needed or config will fail. Turn this option of in this case.
+
+    MINIZIP_INSTALL=ON -- Enable installation of minizip
+
+    MINIZIP_INSTALL_COMPAT_DLL=ON -- Install a copy as libminizip-1.dll
+
+This option is only available on mingw as they tend to name this lib different. Maybe this will also be
+removed in the future as. If you rely cmake for finding and using zlib, this can be turned off, as
+the other file will never be used.
+
+## Using the libs ##
+
+To pull in what you need it's enough to just write
+
+    find_package(ZLIB CONFIG)
+
+or
+
+    find_package(minizip CONFIG)
+
+in your CMakeLists.txt, however it is advised to specify what you really want via:
+
+    find_package(ZLIB CONFIG COMPONENTS shared static REQUIRED)
+
+or
+
+    find_package(minizip CONFIG COMPONENTS shared static REQUIRED)
+
+As it's possible to only build the shared or the static lib, you can make sure that everything you need
+is found. If no COMPONENTS are requested, everything that is found will satisfy your request. If the
+libraries are optional in you project, you can omit the REQUIRED and check yourself if the targets you
+want to link against are created.
+
+When you search for minizip, it will search zlib for you, so only one of both is needed.
+
+## Imported targets ##
+
+When found the following targets are created for you:
+
+    ZLIB::ZLIB and ZLIB::ZLIBSTATIC -- for zlib
+    MINIZIP::minizip and MINIZIP::minizipstatic -- for minizip