v2.1.0

• #64 Switch from Travis to GitHub Actions (@pamil)
• #65 Remove PHPStan (@pamil)
• #66 Upgrade to Psalm 4 (@pamil)
• #67 Update dependencies (@pamil)
• #68 Add tests for symfony/translation-contracts ^1.1 and ^2.0 (@pamil, @dpfaffenbauer)
• #69 Normalise composer.json (@pamil)