Add Plural Safe-Outputs Support

Adds support for plural forms in safe-outputs configuration to allow creating multiple issues and comments in a single workflow execution.

Key Changes

New Syntax:

• create-issues (plural) with optional max parameter (default: 10)
• add-issue-comments (plural) with optional max parameter (default: 10)
• create-pull-request remains singular-only (max: 1)

Configuration Examples:

safe-outputs:
  create-issues:
    max: 3           # Custom limit
  add-issue-comments: # Uses default max: 10
  create-pull-request: # Always max: 1

Implementation:

Updated Go parser to handle both singular/plural forms with early normalization
Enhanced JavaScript validation to respect config-specified max values
Modified processing scripts to handle arrays of items
Extended JSON schema validation
Full backward compatibility maintained
Testing:

1572 Go tests passing
160 JavaScript tests passing
Comprehensive test coverage for new functionality
All existing workflows continue working unchanged.