Update first line indentation

[vkbo]

Summary:

This PR:

• Moves the processing of first line indentation to the Tokenizer class, and removes the logic from the ToOdt class.
• Adds first line indent support to the ToQTextDocument class so The Manuscript preview can show it.

Related Issue(s):

Closes #1858
Closes #1839

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