Fix: migrate global git-ignore into local git-ignores (#224)

The global .gitignore was enforcing files to be ignored in all
sub-projects in the repository.
In order to decouple the dependency of sub-projects on some global
.gitignore convention, removed the global .gitgnore and migrated it to
the corresponding local sub-project within the repository.

PS. The global gitignore was messing with the github action to update
the data. [ref. check the error message on this data update action
run](https://github.com/US-GHG-Center/custom-interfaces/actions/runs/14185180756/job/39739109466)

Author: sanzog03