Improve string access information

[AngelOnFira]

In the list file, information about accessing strings is written as follows:

### Access

```python
example_list [-1] # Backwards accessing
example_list [2:5] # Third, Fourth and Fifth item 
example_list [2:] # Access from third time to the end of the list

This section would do well with more information about parsing strings, splitting strings, and otherwise getting information out of them.