feat: Adds thermal balance point, still need to implement economic balance point.

Sources/Routes/String+double.swift

@@ -1,17 +1,10 @@
 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))!)
+    appendInterpolation(formatter.string(from: NSNumber(value: double))!)
   }
 }