doc: Build from source instruction does not work

[gau-nernst]

On my Mac M1, the following instructions do not work

git clone https://github.com/janhq/cortex.cpp
cd cortex.cpp
git submodule update --init --recursive
cd engine/vcpkg && ./bootstrap-vcpkg.sh
cd ../build && cmake .. && make -j4

One obvious bug is that build/ directory does not exist, and it must be created before the last step. After creating build/ directory, I faced with missing jsoncpp

CMake Error at cli/CMakeLists.txt:62 (find_package):
  Could not find a package configuration file provided by "jsoncpp" with any
  of the following names:

    jsoncppConfig.cmake
    jsoncpp-config.cmake

  Add the installation prefix of "jsoncpp" to CMAKE_PREFIX_PATH or set
  "jsoncpp_DIR" to a directory containing one of the above files.  If
  "jsoncpp" provides a separate development package or SDK, be sure it has
  been installed.

At a glance into our Macos build CI https://github.com/janhq/cortex.cpp/blob/dev/.github/workflows/template-build-macos.yml, there are some differences in the command used. Can we update the correct instructions, and possibly considate the build commands for README and CI, so that there is a single source of truth?