feat: Adds attic ventilation calculation.

Sources/Routes/String+double.swift

@@ -0,0 +1,17 @@
+import Foundation
+
+private let numberFormatter: NumberFormatter = {
+  let formatter = NumberFormatter()
+  formatter.numberStyle = .decimal
+  formatter.maximumFractionDigits = 2
+  return formatter
+}()
+
+public extension String.StringInterpolation {
+  mutating func appendInterpolation(double: Double, fractionDigits: Int = 2) {
+    let formatter = NumberFormatter()
+    formatter.numberStyle = .decimal
+    formatter.maximumFractionDigits = fractionDigits
+    appendInterpolation(numberFormatter.string(from: NSNumber(value: double))!)
+  }
+}