Add cdk8s import just command, exclude cdk8s imports from pre-commit

[MatthewCane]

Describe your changes

• Add import-cdk8s command to Justfile for importing cdk8s resources
• Adjust pre-commit configuration to exclude imports directory for linting and typechecking

Checklist before requesting a review

• I have performed a self-review of my code
• I have updated the Readme / docs
• If this is a breaking change, I have discussed the roll-out and roll-back plan with the team(s) and I have provided detailed instructions
• If it is a core feature, I have added thorough tests