Add GitHub Sponsors funding configuration

[jsirish]

Add GitHub Sponsors Funding Configuration

This issue tracks adding GitHub Sponsors support to make it easier for users to support our open source work.

Tasks

• Create .github/FUNDING.yml with github: [dynamic]
• Add GitHub Sponsors badge to README (same line as CI badge)
• Remove codecov badge if present on CI badge line
• Add composer funding field to composer.json
• Disable phpcoverage in CI workflow if it's failing
• Create PR with all changes

Implementation Details

1. FUNDING.yml

Create .github/FUNDING.yml:

github: [dynamic]

2. README Badge

Add sponsor badge on the same line as CI badge:

[![CI](https://github.com/dynamic/silverstripe-elemental-tabset/actions/workflows/ci.yml/badge.svg)](https://github.com/dynamic/silverstripe-elemental-tabset/actions/workflows/ci.yml) [![Sponsors](https://img.shields.io/badge/GitHub-Sponsors-ff69b4?logo=github)](https://github.com/sponsors/dynamic)

Remove codecov badge if present on that line.

3. Composer Funding

Add to composer.json after the "authors" section:

    "funding": [
        {
            "type": "github",
            "url": "https://github.com/sponsors/dynamic"
        }
    ],

4. CI Workflow (if phpcoverage failing)

If CI has phpcoverage failures, update .github/workflows/ci.yml:

• Change phpcoverage: true to phpcoverage: false
• Or remove codecov upload steps if custom workflow

5. PR Details

Create PR with title: "Add GitHub Sponsors funding configuration"

PR body template:

This PR adds GitHub Sponsors support to make it easier for users to support our open source work.

## Changes
- Added `.github/FUNDING.yml` to enable the GitHub Sponsors button in the repository header
- Added GitHub Sponsors badge to README for better visibility
- Added composer funding field for `composer fund` command support
- Points to [@dynamic](https://github.com/sponsors/dynamic) organization sponsors page

## Benefits
- Provides multiple touchpoints for GitHub Sponsors visibility
- Makes it easier for users to support the project
- Aligns with other Dynamic repositories

The badge will appear at the top of the README alongside existing CI/quality badges.

Success Criteria

• Sponsors button appears in repo header
• README badge displays correctly on CI line
• composer fund shows GitHub Sponsors link
• All CI checks pass
• PR ready for review

References

• GitHub Sponsors: https://github.com/sponsors/dynamic
• Example PRs:
  • Add GitHub Sponsors funding configuration silverstripe-country-dropdown-field#14
  • Add GitHub Sponsors funding configuration silverstripe-elemental-blog#51
  • Add GitHub Sponsors funding configuration silverstripe-elemental-accordion#49