chore: add .idea folder to .gitignore file

Added the .idea folder to the .gitignore file to avoid not pushing the Jetbrain IDEs projects configuration.

Checklist

[x] I have read the contributing guidelines and signed the CLA.
[ ] I have referenced an issue containing the design document if my change introduces a new feature.
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[ ] I have added tests that prove my fix is effective or that my feature works.
[ ] I have added the necessary documentation within the code base (if appropriate).