Adding venn4, a function for creating Venn diagram for four sets

[farid-zare]

I hereby confirm that I have: This is a code from this repo: https://github.com/manhowong/matlab-venn/tree/main For creating Venn diagrams for four sets Since a function name "Venn" already exist in MATLAB, I had to change the name to venn4. So it's not possible to add this as a submodule.

• [x] Tested my code on my own machine
• [x] Followed the guidelines in the Contributing Guide
• [x] Selected develop as a target branch (top left drop-down menu)