Update the readme to include more details about compiling and running

**Is your feature request related to a problem? Please describe.**
Currently, the readme doesn't provide a step by step instruction on how to build the Pythia8 environment and subsequent compilation and post-processing with afterburner

**Describe the solution you'd like**
Steps to reproduce production data:
1) Run eic-shell or an environment that has access to hepmc.

2)
Clone generator file
```
git clone https://gitlab.com/eic/LambdaGen.git --branch pythia8.306-1.0 --single-branch
```
3)
Clone and make Pythia 8
```
git clone https://gitlab.com/Pythia8/releases.git --branch pythia8306 --single-branch
cd releases
./configure --with-hepmc3
make
```
4)
Build and run generator
```
cd bin
g++ ../../LambdaGen/main41_Lam.cc -o main41_Lam `pythia8-config --cflags --libs --hepmc3`
./main41_Lam
```
5)
Take the generated outputs and run afterburner with the right setting for example
```
abconv -p ip6_hidiv_275x18 hepmc_Lambda1.dat
```

Additional context, such as what's a good number of events to simulate will also be helpful

**Describe alternatives you've considered**

**Additional context**