Add .gitattributes with export-ignore patterns

[CybotTM]

Description

Add .gitattributes file to reduce the size of releases by excluding development files from exported archives (Composer/TER releases).

Current State

• No .gitattributes file present
• Development files included in releases (tests, CI configs, docs build files)
• Larger than necessary release archives

Proposed Changes

Create .gitattributes with the following content:

# Exclude development files from exports
/.github export-ignore
/.ddev export-ignore
/Tests export-ignore
/Build export-ignore
/.gitignore export-ignore
/Documentation-GENERATED-temp export-ignore
/renovate.json export-ignore
/.editorconfig export-ignore
/AGENTS.md export-ignore
/Makefile export-ignore
/.envrc export-ignore
/.crowdin.yml export-ignore

Benefits

• Smaller release archives
• Faster Composer installations
• Cleaner TER releases
• Professional package management

Acceptance Criteria

• .gitattributes file created with export-ignore patterns
• Test with git archive to verify exclusions work
• Verify next release is smaller

Priority

Low - Nice to have, minimal effort

Related

TYPO3 Conformance Report: Excellence Indicators +1 point