chore(github): add issue templates

[mstykow]

Summary

• add simple label-driven GitHub issue templates for bugs, feature requests, documentation issues, and questions
• disable blank issues so reports use the intended templates instead of free-form issue bodies
• order the templates so the chooser shows bug, feature, documentation, then question

Scope and exclusions

• Included: .github/ISSUE_TEMPLATE/ metadata only
• Explicit exclusions: issue forms, contact links, GitHub Discussions routing, and workflow changes

Follow-up work

• Created or intentionally deferred: optional contact_links if maintainers later want to route support or security traffic outside issues