Added bitwiseAND function for bitwise AND operation

src/main/c/main_taschenrechner.c

@@ -62,6 +62,11 @@ double exponentialFunction(double x) {
     return exp(x);
 }
 
+// ..
+// Bitwise AND function
+int bitwiseAND(int num1, int num2) {
+    return num1 & num2;
+}
 
 // scientificmode
 int scientificMode(){

src/main/c/taschenrechner.h

@@ -28,6 +28,10 @@ double logarithmBase2Function(double x);
 // Exponential function
 double exponentialFunction(double x);
 
+// ..
+// Bitwise AND function
+int bitwiseAND(int num1, int num2);
+
 int mode(int userChoice);
 
 int displayMenu();