add Chapter 15 - runtime observer implementation

Chapter15/observer/libs/etl/arduino/examples/Example_0_import_etl/Example_0_import_etl.ino

@@ -0,0 +1,12 @@
+#include "Embedded_Template_Library.h"  // This is required for any more etl import when using Arduino IDE
+
+void setup()
+{
+  
+}
+
+
+void loop()
+{
+  
+}

Chapter15/observer/libs/etl/arduino/examples/Vector_Examples/Example_Vector_1_simple_use/Example_Vector_1_simple_use.ino

@@ -0,0 +1,46 @@
+// make sure that we do not rely on the STL
+#define ETL_NO_STL
+
+#include "Embedded_Template_Library.h"
+#include "etl/vector.h"
+
+template <typename T>
+void print_vector(etl::ivector<T> const & vec_in)
+{
+  Serial.print(F("print vector content | size ")); Serial.print(vec_in.size()); Serial.print(F(" | capacity ")); Serial.println(vec_in.capacity());
+  Serial.print(F("content | "));
+
+  for (T const & elem : vec_in) 
+  {
+    Serial.print(elem);
+    Serial.print(F(" | "));
+  }
+
+  Serial.println();
+}
+
+void setup()
+{
+  Serial.begin(115200);
+  delay(100);
+  Serial.println(F("booted"));
+
+  etl::vector<int, 12> vec_int;
+
+  Serial.println(F("initialized vec_int"));
+  print_vector(vec_int);
+
+  vec_int.push_back(1);
+  vec_int.push_back(2);
+  Serial.println(F("pushed to vec_int"));
+  print_vector(vec_int);
+
+  vec_int.pop_back();
+  Serial.println(F("pop from vec_int; returns no value"));
+  print_vector(vec_int);
+}
+
+void loop()
+{
+  
+}