Added children count label next to the node key

[VladCuciureanu]

Implements #169

• Adds children count label next to text node key
• Adds option to toggle visibility of children count label

[AykutSarac]

Thanks for your contribution! Can we follow the following issues before the merge? :)

• Hide number of children and remove odd paddings from parent if there are no child
• Can we reduce margin-left from -12px to -15px?
• Disable showing child number by default at settings

Thank you!!

[VladCuciureanu]

Thanks for your contribution! Can we follow the following issues before the merge? :)

• Hide number of children and remove odd paddings from parent if there are no child
• Can we reduce margin-left from -12px to -15px?
• Disable showing child number by default at settings

Thank you!!

Fixed. Please tell me if there are any further needed modifications.