Comply to new ESLint rules

src/erasure.js

@@ -19,9 +19,9 @@ function cap01(x) {
 }
 
 function distToSegmentSquared(lineStart, lineEnd, point) {
-  var l2 = distanceSquared(lineStart, lineEnd)
+  const l2 = distanceSquared(lineStart, lineEnd)
   if (l2 === 0) return distanceSquared(point, lineStart)
-  var t =
+  let t =
     ((point[0] - lineStart[0]) * (lineEnd[0] - lineStart[0]) +
       (point[1] - lineStart[1]) * (lineEnd[1] - lineStart[1])) /
     l2
@@ -100,7 +100,7 @@ function mergeIntervals(...intervals) {
   if (!intervals.length) return []
 
   const sorted = intervals.sort(([a], [b]) => a > b)
-  let stack = [sorted[0]]
+  const stack = [sorted[0]]
   sorted.forEach((x) => {
     const top = stack[stack.length - 1]
     if (overlaps(x, top)) {