Add fixture 'gruft/pixel-tube'

[FloEdelmann]

• Add fixture 'gruft/pixel-tube'
• Update register.json

Fixture warnings / errors

• gruft/pixel-tube
  • :x: File does not match schema. [ { keyword: 'pattern', dataPath: '.availableChannels', schemaPath: '#/properties/availableChannels/propertyNames/pattern', params: { pattern: '^[^$\n]+$' }, message: 'should match pattern "^[^$\n]+$"', propertyName: 'Intensity $pixelKey' }, { keyword: 'propertyNames', dataPath: '.availableChannels', schemaPath: '#/properties/availableChannels/propertyNames', params: { propertyName: 'Intensity $pixelKey' }, message: 'property name \'Intensity $pixelKey\' is invalid' } ]

Thank you @FloEdelmann!