Version 3.4.0 released

The latest version of renpy-encyclopaedia adds a new container object called Book. This is a new way to link multiple entries together. It has a similar purpose to Sub-Pages but has more features.

Full documentation for it is available at: https://renpy-encyclopaedia.readthedocs.io/en/stable/

Added 

 - Book object for grouping EncEntry. 

 Changed 

- `AddEntryError` is raised when adding an entry fails, instead of ValueError.

 - The attribute EncEntry.has_pages has been removed. Use `len(EncEntry().pages) > 1` instead. 

- The method `Encyclopaedia.add_entry_to_unlocked_entries()` is now private and renamed to `Encyclopaedia._add_entry_to_unlocked_entries()` 

- The method `EncEntry.add_entry_to_unlocked_entries()` is now private and renamed to `EncEntry._add_entry_to_unlocked_entries()`