Exercise 5 & updated README

Added Exercise 5 and translated README and added signature as well as
disclaimer

Informatik_I/Exercise_5/Task_3/README.md

@@ -0,0 +1,28 @@
+_This task is a text based task. You do not need to write any program/C++ file: the answer should be written in main.md (and might include code fragments if questions ask for them)._
+
+# Task:
+
+What are the problems (if any) with the following functions? Fix them and find appropriate [pre-](https://en.wikipedia.org/wiki/Precondition) and [postconditions](https://en.wikipedia.org/wiki/Postcondition).
+
+1. function is_even:
+
+```cpp
+
+bool is_even(int i) {
+    if (i % 2 == 0) return true;
+}
+```
+
+1. function invert:
+
+```cpp
+double invert(int x) {
+    double result;
+    if (x != 0) {
+        result = 1.0 / x;
+    }
+    return result;
+}
+```
+
+**Hint**: The C++ compiler does not protect you from certain types of errors. Therefore, even if you run a program in Code Expert, it is not guaranteed that the behaviour you observe is the “real” one. We have prepared a [program tracing handout](https://lec.inf.ethz.ch/ifmp/2023/guides/tracing/intro.html) that shows how to execute a program with a pen and paper and which conditions indicate bugs in the executed program not caught by the C++ compiler.