Adding Contributors

This issue is to add major contributors to TIGRE.

My approximate unscientific parameter is that if you have added a significant feature (i.e. not typos) and/or have done more than +500 lines of code, you are automatically in! Comment below and I will invoke the bot.

However, any improvement is very well received, and your name will always be in https://github.com/CERN/TIGRE/graphs/contributors . I thank all of you, even the smallest commit, for making TIGRE a reality.