Add .idea to .gitignore

[mtjhrc]

Summary of the PR

".idea" directories are produced by JetBrains RustRover IDE, ignore them like we do with ".vscode".

Requirements

Before submitting your PR, please make sure you addressed the following
requirements:

• All commits in this PR have Signed-Off-By trailers (with
  git commit -s), and the commit message has max 60 characters for the
  summary and max 75 characters for each description line.
• All added/changed functionality has a corresponding unit/integration
  test.
• All added/changed public-facing functionality has entries in the "Upcoming
  Release" section of CHANGELOG.md (if no such section exists, please create one).
• Any newly added unsafe code is properly documented.

[epilys]

Personally I put custom ignore rules in a global exclude file with the core.excludesfile in my gitconfig. You can even do it per repository tree by adding ignore rules in .git/info/exclude. I don't have a strong opinion or opposition to this change, it just seems that personal software-related changes should not be committed to a repository just like we shouldn't commit .vscode and .idea either.

It doesn't make a difference though, feel free to merge.

[stefano-garzarella]

@epilys I agree with you, I accepted just because we already have .vscode

[mtjhrc]

I don't have a strong opinion or opposition to this change, it just seems that personal software-related changes should not be committed to a repository just like we shouldn't commit .vscode and .idea either.

Yeah, that makes sense. I don't really care that much about this either.

I saw .vscode there, so I though I might as well add this too. Also the rust-vmm/vhost repo has .idea https://github.com/rust-vmm/vhost/blob/main/.gitignore .