Generate documentation

Doxygen documentation is available online.

It is also possible to generate Doxygen documentation locally:

Install Doxygen or use bailool/mc-calib-dev docker image:

sudo apt install flex
sudo apt install bison
git clone https://github.com/doxygen/doxygen.git
cd doxygen
mkdir build
cd build
cmake -G "Unix Makefiles" ..
make
make install # optional

Doxygen is already added to the CmakeLists.txt and is auto-generated if dependencies are satisfied. However, it is also possible to set it up manually:
```
mkdir docs
cd docs
doxygen -g
#set INPUT = ../src in Doxyfile
doxygen
```