Docs(coordinator): update instruction of the coordinator

[kittybest]

Description
I'm not sure where to provide instructions on how to use the entire repository, but theoretically, the process should look like this:

1. install and build
2. especially need to run build command inside the contracts package
3. run download-zkeys command either in the root or the coordinator package
4. update the deploy-config.json file inside the contracts package
5. deploy basic maci contracts inside the contracts package
6. go to coordinator package, set up the round-metadata.json file and run the upload-round-metadata command
7. go to subgraph package, set up the network.json file and run the commands inside the README.md file
8. update the deploy-config.json again, then deploy-poll inside the contracts package

How do you think where should we update these instructions?