chore: Add issue template

[karangattu]

This pull request introduces new issue templates for bug reports, documentation issues, and feature requests to improve the process of reporting and managing issues in the Shiny for Python project. The most important changes include the addition of structured forms with required fields and detailed instructions to ensure comprehensive and clear issue submissions.

New Issue Templates:

• Bug Report Template:

  • Added a structured form to gather detailed information about bugs, including the affected component, severity, Shiny and Python versions, minimal reproducible example, current and expected behavior, error messages, environment information, and additional context.

• Documentation Issue Template:

  • Introduced a template to report documentation issues or suggest improvements, with fields for documentation type, location, issue type, current content, suggested changes, motivation, additional context, and preliminary checks.

• Feature Request Template:

  • Created a form to suggest new features, including fields for feature category, scope, problem description, proposed solution, alternative solutions, example usage, expected impact, implementation considerations, complexity estimate, and preliminary checks.