Add vcpkg support

Summary

While exploring vcpkg I realized that with Conan 2 it should be possible to actually offer both Conan and vcpkg as package managers. This MR brings support for compilation with vcpkg to the cpplib.

Related to #81 (closed)

Focus

• A few files were added to support vcpkg, and some changes had to be made to the CMakeLists.txt file to make it compatible with both Conan 2 and vcpkg.
• Instructions on how to build with vcpkg can be found in docs/Install_develop.rst.
• A GitLab CI step to test building with vcpkg was added to the pipeline.

Test Environment

Follow new build instructions to test vcpkg.

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doc/Install_develop.rst

@@ -19,6 +19,27 @@ which have ``make`` installed, type this in your command line terminal:
 
    make conan
 
+Building with ``vcpkg``
+~~~~~~~~~~~~~~~~~~~~~~~
+
+You can use the vcpkg package manager to install the dependencies (`vcpkg.json`). It's included as 
+a submodule in the project. To install the dependencies, run the following commands:
+
+.. code:: console
+
+   ./vcpkg/bootstrap-vcpkg.<sh/bat>
+   vcpkg/vcpkg install
+
+
+Then compile the project with CMake by including the vcpkg toolchain file:
+
+.. code:: console
+
+   cd build
+   cmake -S .. -B . -DCMAKE_TOOLCHAIN_FILE=../vcpkg/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-linux 
+   cmake --build .
+
+
 Manual build
 ~~~~~~~~~~~~
 
@@ -74,7 +95,7 @@ as compiler. We use `cmake <https://cmake.org/download/>`__ as build
 tool.
 
 1. clone/update the subrepo ``git submodule update --init proto``
-2. ``conan install .. -g visual_studio -s arch=x86_64 -s build_type=Release -s compiler.toolset=v142 -s compiler.version=16 -s compiler.runtime=MD --build=missing --update``
+2. :code:``conan install .. -g visual_studio -s arch=x86_64 -s build_type=Release -s compiler.toolset=v142 -s compiler.version=16 -s compiler.runtime=MD --build=missing --update``
 3. ``cd build/Release``
 5. ``cmake -B . ..``
 6. open ``libcaosdb.sln`` with Visual Studio, change the buildtype to