add/update keybindings for neotree window size manipulation

[sepisoad]

• add key binding "=" to enlarge neotree window
• add key binding "-" to shrink neotree window
• add key binding "0" to reset neotree window
• renamed original keybinding "-" to "h"
• renamed original keybinding "|" to "v"

[Abdisalan]

Existing keybinding are staying the same so we don't affect other users outside a major update. And the zoom settings are there for configuration and are usually covered and not a focus for this package. Example: text-scale-increase is set to C-x C-= or just C-= in evil mode. Thanks for taking the time though