Add module speed diagram into docs.

doc-dev/reference-manual.md

@@ -409,7 +409,7 @@ For the purpose of toggling functionality on and off, and for global constants m
   - `deceleratedSpeed` - speed as affected by deceleration modifier
   - `acceleratedSpeed` - speed as affected by acceleration modifier
   - `axisSkew` - axis skew multiplies horizontal axis and divides vertical. Default value is 1.0, reasonable between 0.5-2.0 Useful for very niche usecases.
-- `set module.MODULEID.{baseSpeed|speed|xceleration}` modifies speed characteristics of right side modules. Simplified formula is `speedMultiplier(normalizedSpeed) = baseSpeed + speed*(normalizedSpeed^xceleration)` where `normalizedSpeed = actualSpeed / midSpeed`. Therefore `appliedDistance(distance d, time t) = d*(baseSpeed*((d/t)/midSpeed) + d*speed*(((d/t)/midSpeed)^xceleration))`. (`d/t` is actual speed in px/s, `(d/t)/midSpeed` is normalizedSpeed which acts as base for the exponent)
+- `set module.MODULEID.{baseSpeed|speed|xceleration}` modifies speed characteristics of right side modules. Simplified formula is `speedMultiplier(normalizedSpeed) = baseSpeed + speed*(normalizedSpeed^xceleration)` where `normalizedSpeed = actualSpeed / midSpeed`. Therefore `appliedDistance(distance d, time t) = d*(baseSpeed*((d/t)/midSpeed) + d*speed*(((d/t)/midSpeed)^xceleration))`. (`d/t` is actual speed in px/s, `(d/t)/midSpeed` is normalizedSpeed which acts as base for the exponent). ![speed relations](resources/mouse_speeds.svg)
   - `baseSpeed` is base speed multiplier which is not affected by xceleration. I.e., if `speed = 0`, then traveled distance is `reportedDistance*baseSpeed`
   - `speed` multiplies effect of xceleration expression. I.e., simply multiplies the reported distance when the actual speed equals `midSpeed`.
   - `xceleration` is exponent applied to the speed normalized w.r.t midSpeed. It makes cursor move relatively slower at low speeds and faster with aggresive swipes. It increases non-linearity of the curve, yet does not alone make the cursor faster and more responsive - thence "xceleration" rather than "acceleration" to avoid confusion. I.e., xceleration expression of the formula is `speed*(reportedSpeed/midSpeed)^(xceleration)`. I.e., no acceleration is xceleration = 0, reasonable (square root) acceleration is xceleration = 0.5. Highest recommended value is 1.0.