Add Little Disciple fire rate to the ItemStats integration

[BLucky-gh]

The Little Disciple fire rate scales with movement speed, and the description specifies the base fire rate, it would be neat if it also showed the calculated fire rate (sorry for fullscreen screenshot, can't win+shift+s while holding tab)

[DestroyedClone]

https://riskofrain2.fandom.com/wiki/Little_Disciple#Math

The time in seconds between each fired wisp is determined by the formula 35 / (3 ⋅ movementSpeed)

This lines up with the in-game component RoR2.Items.SprintWispBodyBehavior, as the fractional value appears to be the same. (https://www.desmos.com/calculator/x71oxoaiwh)

1f / (SprintWispBodyBehavior.fireRate * base.body.moveSpeed);
...
private static readonly float fireRate = 0.08571429f;