cmake jsoncpp linking error

Hi, I have a feeling that jsoncpp library is incorrectly called in a CMakeLists.txt, resulting in a linking errors, the issue being that due to case sensitivity in pkg-config, it is incapable of finding Jsoncpp and linking Jsoncpp_lib.

**To Reproduce**
Steps to reproduce the behavior:
1. Clone the repository
2. mkdir build && cd build && cmake .. && make
3. See error

**Expected behavior**
Code/drogon library links successfully against jsoncpp library

**Environments tested**
1. jsoncpp and jsoncpp-devel installed via dnf
2. jsoncpp compiled from source (checked out to 1.9.6) https://github.com/open-source-parsers/jsoncpp

OS version: Fedora 39, 6.5.6-300.fc39.x86_64
gcc (GCC) 13.3.1 20240913 (Red Hat 13.3.1-3)
cmake version 3.30.5
pkg-config --version 1.9.5

**Additional context**
For me, the fix was rewriting the CMakeLists.txt lines 190 and 191 using lowercase (to jsoncpp and jsoncpp_lib respectively). In case of meeting the same issue, modifying the cmakelists should do the trick, but feel free to ping me.