Add ignores for Linux CMake systems

[martinlyra]

A PR intended to improve the quality of life for users with Linux systems and CMake + make. Since the CMake and make systems generate build maps and compiled objects that are not covered by the git-ignore file. In my case I just ran cmake . in the repository's root to get started on the assignments immediately.

The changes were adding two different git-ignore templates to the repo's git-ignore - from the public repository here: https://github.com/github/gitignore

Before:

After:

[pierremoreau]

Why not use a dedicated build folder as recommended, instead of building inside the source folder?
That way you avoid the clutter from build artefacts, and removing all those artefacts becomes as simple as deleting the whole build folder.

[martinlyra]

Looking back on the READMEs, I've missed reading the guide on getting started with building because I was skimming on them, so I just ran cmake . to start immediately with the assignments. It suited me fine working with the terminal and Visual Studio Code without a second thought on it.

Additionally git clean -X can clean the local repository off ignored files.