Page that lists the contributors for each year

[alexpearce]

From @ibab in lhcb/first-analysis-steps#155:

Makes it easier to find out who helped and instructed and gives everyone a fuzzy feeling

[kdungs]

There are two separate issues, namely #15 and #25, that have been stale for quite a while now. Dealing with them would also mean listing the helpers and contributors just as https://lhcb.github.io/starterkit/archive/starterkit/2015/06/02/starterkit1.html does.