Change code style to have open curly braces in the same line

Background

With issue adblockpluscore#311 (closed) (MR adblockpluscore!472 (merged)) adblockpluscore moved to have a code style closer to the common JavaScript usage by having the opening curly brace on the same line.

Use case

This change of style will make it easier for various tools/editors to auto format the code.

What to change

• Change the eslint rules.
• Run eslint --fix to apply the new rule.