refactor: apply psr-12-extended-coding-style

[grandeljay]

As described in the PSR-12 Extended Coding Style Guide, I have made the following changes/corrections:

1. When instantiating a new class, parentheses MUST always be present even when there are no arguments passed to the constructor.

2. The opening brace for the class MUST go on its own line; the closing brace for the class MUST go on the next line after the body.

The spaces around the concentration operator are not required but I have added for increased readability.

[freekmurze]

Thanks! I'm going to leave it like it is for now.