Add iteration issue template

[annezazu]

Summary

• Adds a new GitHub issue template for iteration/release cycle tracking
• Standardizes the format already used across existing [Type] Iteration issues (e.g. Client Side Media iteration for WordPress 7.1 #76756, Block Supports and design tools in WordPress 7.1 #76525, Notes iteration for WordPress 7.1 #76316) into a reusable template
• Includes sections for: Overall Goal, Scope for This Release, Tasks (as checklists), and Nice to Have (stretch goals)
• Auto-applies the [Type] Iteration label

Test plan

• Verify the template appears when creating a new issue at https://github.com/WordPress/gutenberg/issues/new/choose
• Confirm the rendered template includes all four sections with placeholder guidance
• Confirm the [Type] Iteration label is auto-applied

🤖 Generated with Claude Code

[github-actions]

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Co-authored-by: annezazu <annezazu@git.wordpress.org>
Co-authored-by: ramonjd <ramonopoly@git.wordpress.org>
Co-authored-by: andrewserong <andrewserong@git.wordpress.org>

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[github-actions]

Flaky tests detected in ffec141.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/24113956664
📝 Reported issues:

• [Flaky Test] post title and content are editable and blocks can be inserted #76524 in /test/e2e/specs/editor/various/post-content-focus-mode.spec.js
• [Flaky Test] should show correct homepage actions based on current homepage or posts page #68892 in /test/e2e/specs/site-editor/homepage-settings.spec.js

[andrewserong]

Just removing one label from this issue to please the Github Action that checks that only one "Type" label is attached 🙂

[andrewserong]

Thanks for this, I don't think we can test before merge, but this LGTM!

(As an aside, love the idea: the comments read well and this looks like a useful guide for contributors to structure planning for iteration issues 👍)

[ramonjd]

I guess we could add a title: to prefill the title field, e.g., title: "[Feature Name] iteration for WordPress X.X"

Not a blocker and can be added later.

[ramonjd]

LGTM. I'll merge it in and test (just created a new iteration issue, so I can add these new headings 🍺 )

Thank you!

[andrewserong]

All looking good after merge:

🎉

[annezazu]

Gosh, thank you all for seeing this through and making it better.