Update minimum Go version in CONTRIBUTING.md doc to 1.18

[dseapy]

Summary

• Updates minimum Go version in CONTRIBUTING.md doc to 1.18
• Adds Jetbrains IDE files to gitignore

Related issue(s)

Fixes #1650

[openshift-ci]

Hi @dseapy. Thanks for your PR.

I'm waiting for a kcp-dev member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[sttts]

Thank you!

/lgtm
/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sttts

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[sttts]

/ok-to-test