Add word stats to manuscript tool

[vkbo]

Summary:

This PR:

• Improves the general word counter and moves it into a new counting module in a text folder. This older will contain more text analysis tools later on.
• Adds an optional stats counter to the Tokenizer class that counts words and characters in the compiled manuscript, as well as counts for headings and body text separately, including words, characters, and characters without spaces.

Related Issue(s):

Closes #1114
Closes #1116

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed