Erro During Pull Request for Leiden University is not in the institution.csv

[Zheng Chen]

Hello,

While running the commit validation, I encountered an error that Leiden University is not listed in the institution.csv.

I would like to provide basic information about Leiden University and its computer department:
Leiden University:https://www.universiteitleiden.nl/en
Leiden Institute of Advanced Computer Science:https://www.universiteitleiden.nl/en/science/computer-science

I'd appreciate it if you could add Leiden University to the file.

If another pull request and validation are needed afterward, I will open another one.