Add a feature to normalize book entries

[DSiekmeier]

Is your feature request related to a problem? Please describe.
There is often a mismatch with the capitalization of book entries. For example sometimes all letters are in lowercase, some are uppercase and so on. This might distract the reader of a book list. It would be nice to have a method to automatically transform the texts and normalize them in a way.

Describe the solution you'd like
A new subcommand modify or transform might be implemented. In a first step it might be sufficient to add options like --title-uppercase and similar. Another step could be to introduce templates for this.