Add `hal::soft::offset_servo` implementation

[kammce]

Take a servo implementation and remap the definition of it position values. For example, take a servo that can move from 0 degs to 90 degs. If an application needs to control a servo from -45 deg to +45 deg, then the offset_servo implementation simply maps 0 to -45 degs and 90 to 45 deg. Making zero 45 degrees. This implementation should be done with addition only as to not distort the range of the input servo.

[Coreyboy1820]

.take