New Run Config field: run.speed.z

[PauloHPBender]

Is your feature request related to a problem? Please describe.
In OpenBoR 4.0, the new feature run.speed.x, along with all the other new configurations, allowed greater freedom for the developer, and yet, I feel that a run.speed.z is lacking.

Describe the solution you'd like
Being able to declare clearly how fast the character is able to move in the Z axis while running.

Describe alternatives you've considered
I've considered zeroing all run config values and creating a custom animation where I could manipulate both X and Z speed, but it seems counterintuitive and a reinventing of the wheel.

Additional context
My current project has characters that run very fast, but with little maneuverability (IOW, high X speed, low Z speed), while others run slower bur with more finesse.

[DCurrent]

@PauloHPBender,

This feature is already in progress for future releases. Part of the code is already done.