New Features

• Load multiple values from a single source with the multiple flag
  • Supported for all value source types
• file value source, which loads value(s) from a file path (combine with multiple = true for maximum fun!)
• Support non-string primitives for simple literal values
  • E.g. VARIABLE1 = 123 or VARIABLE2 = false
  • These values will simply be stringified before export, since shells only understand strings anyway

Other

• Improve test coverage!