Remove .DS_Store in src directory

[CaroFG]

We should create a .gitignore file and add it too

[Shivay Lamba]

@CaroFG in my PR, I removed the .DS_Store in the src directory but yes in general we should create a gitignore file for any demo we want to add to the demos repository. Something like a starter template for demos

[CaroFG]

Each demo has its own .gitignore, but it doesn't apply to the demos repository, we should create a general .gitignore to avoid pushing unwanted files to the root or the src directories