Add Titanic example and improve optional type to be usable with str type (#39)

* add example for titanic code

* improve the optional type from pandantic

* adjust test to check for optional str

* add titanic csv

* exception for titanic csv for exmaple

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Co-authored-by: Wessel Huising <wessel.huising@mollie.com>

Author: wesselhuising

.gitignore

@@ -1,6 +1,7 @@
 # Project specific
 *.code-workspace
 *.csv
+!titanic.csv
 *.DS_Store
 
 # Byte-compiled / optimized / DLL files