Add subscript to issue templates

[Copilot]

This PR adds a subscript dropdown to the bottom of each issue template to help users understand issue prioritization and community participation guidelines.

Changes Made

Added a YAML dropdown element to the bottom of both issue templates:

• .github/ISSUE_TEMPLATE/bug_report.yml
• .github/ISSUE_TEMPLATE/feature_request.yml

The subscript includes:

• Instructions to react with 👍 to help prioritize issues
• Guidelines to use comments for useful context rather than +1 or me too
• Link to community participation documentation

Implementation Details

The subscript was implemented as a dropdown element with:

• Label: "Tip"
• Static description explaining its purpose
• Single option containing the subscript text with HTML <sub> formatting
• Default value of 0 (automatically selects the tip)
• Clear instructions for maintainers to leave as-is

Example

The subscript renders as:

Tip
_{React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it. Learn more here.}

This implementation follows the exact specifications provided in the issue and makes minimal changes to the existing templates.

Fixes #42.

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