fix: move swift-tools-version to first line of Package.swift

[SalihCanBinboga]

Swift 6.0+ requires the swift-tools-version declaration to be on the very first
line of Package.swift. The current file has a copyright header before it, which
causes Xcode (Swift 6.0+) to fail with:

the manifest is backward-incompatible with Swift < 6.0 because the tools-version
was specified in a subsequent line of the manifest, not the first line.

This moves the // swift-tools-version: 5.9 comment to line 1, before the copyright
header, following the Swift Package Manager specification.

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[nstosic]

I'm running into the same issue, so I also want to raise urgency on getting this merged and published

[Copilot]

Pull request overview

Updates the Swift Package manifest header ordering to comply with Swift 6.0+ requirements that the swift-tools-version declaration appear on the very first line of Package.swift, preventing Xcode/SwiftPM manifest compatibility errors.

Changes:

• Moved // swift-tools-version: 5.9 to line 1 in ios/facebook_app_events/Package.swift.
• Kept the existing copyright/license header immediately after the tools version line.

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[DennisAlund]

See: https://pub.dev/packages/facebook_app_events/versions/0.26.1