feat: Add no-duplicate-imports rule

[nzakas]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

Add a new no-duplicate-imports rule.

What changes did you make? (Give an overview)

• Created no-duplicate-imports rule
• Added tests for the rule
• Added docs for the rule

Related Issues

Is there anything you'd like reviewers to focus on?

[mdjermanovic]

We should also add the new rule to plugin.rules, recommended config, and README.

[mdjermanovic]

We should add the rule here as well:

css/src/index.js

Lines 26 to 28 in c9424e5

	rules: {
	"no-empty-blocks": noEmptyBlocks,
	},

[mdjermanovic]

LGTM, thanks!