Support room-defined height as well

Much like widget widths, it is acceptable for us to forget what everyone's height was previously at.

src/utils/numbers.ts

@@ -32,3 +32,11 @@ export function clamp(i: number, min: number, max: number): number {
 export function sum(...i: number[]): number {
     return [...i].reduce((p, c) => c + p, 0);
 }
+
+export function percentageWithin(pct: number, min: number, max: number): number {
+    return (pct * (max - min)) + min;
+}
+
+export function percentageOf(val: number, min: number, max: number): number {
+    return (val - min) / max;
+}