Add list of papers that use TIGRE

Somewhere in the frontispiece. Also edit Readme on how to submit yours.

This would help TIGRE, but I believe would also help a lot the researchers that use it, to have more exposure to their work.

Start by locating the frontispiece and the repository README. Review how existing papers or citations are presented, then add a list of papers that use TIGRE and document how researchers can submit their papers. Done means both locations contain the requested information and the submission instructions are clear.

Written by the indexing model from the issue text.