Add stubs for printing FloatingPoints (#71)

Sources/CPlaydate/include/CPlaydate.h

@@ -1,2 +1,10 @@
 #pragma once
 #include "pd_api.h"
+
+int formatStringFloat(PlaydateAPI p, char **outstring, float number) {
+    return p.system->formatString(outstring, "%f", number);
+}
+
+int formatStringDouble(PlaydateAPI p, char **outstring, double number) {
+    return p.system->formatString(outstring, "%lf", number);
+}

Sources/PlaydateKit/Utils/FloatingPoint+CustomStringConvertible.swift

@@ -0,0 +1,24 @@
+// TODO: - Temporary workaround until FloatingPoint print support is added to Embedded Swift
+import CPlaydate
+
+// MARK: - Float + CustomStringConvertible
+
+extension Float: @retroactive CustomStringConvertible {
+    public var description: String {
+        var outString: UnsafeMutablePointer<CChar>?
+        formatStringFloat(Playdate.playdateAPI, &outString, self)
+        defer { outString?.deallocate() }
+        return String(cString: outString!)
+    }
+}
+
+// MARK: - Double + CustomStringConvertible
+
+extension Double: @retroactive CustomStringConvertible {
+    public var description: String {
+        var outString: UnsafeMutablePointer<CChar>?
+        formatStringDouble(Playdate.playdateAPI, &outString, self)
+        defer { outString?.deallocate() }
+        return String(cString: outString!)
+    }
+}