Move math and random files into their respective modules (#198)

* Move math and random files into their respective modules

- Move distanceBetweenPointAndSegment to math module
- Move LCG, randomSeed, and withCustomMathRandom to random module

* Add everything else back

src/math.ts

@@ -0,0 +1,38 @@
+// https://stackoverflow.com/a/6853926/232122
+export function distanceBetweenPointAndSegment(
+  x: number,
+  y: number,
+  x1: number,
+  y1: number,
+  x2: number,
+  y2: number
+) {
+  const A = x - x1;
+  const B = y - y1;
+  const C = x2 - x1;
+  const D = y2 - y1;
+
+  const dot = A * C + B * D;
+  const lenSquare = C * C + D * D;
+  let param = -1;
+  if (lenSquare !== 0) {
+    // in case of 0 length line
+    param = dot / lenSquare;
+  }
+
+  let xx, yy;
+  if (param < 0) {
+    xx = x1;
+    yy = y1;
+  } else if (param > 1) {
+    xx = x2;
+    yy = y2;
+  } else {
+    xx = x1 + param * C;
+    yy = y1 + param * D;
+  }
+
+  const dx = x - xx;
+  const dy = y - yy;
+  return Math.hypot(dx, dy);
+}