Add prerequisites section

README.md

@@ -5,3 +5,13 @@ in programming with **[Python <img height="12" style="display: inline-block" src
 
 The **main goal** is to **prepare** students
 for **further studies** in the "field" of **data science**.
+
+
+### Prerequisites
+
+To be suitable for *beginners*, there are *no* formal prerequisites.
+It is only expected that the student has:
+- a *solid* understanding of the **English** language,
+- knowledge of **basic mathematics** from high school,
+- the ability to **think conceptually** and **reason logically**, and
+- the willingness to **invest** around **90-120 hours** on this course.