dcrochu as of 20/02/2024, plus rsigns and typo standardization. Added a missing virga in NABC

Added altera pars incipit following addition of the annotation which breaks the tight typesetting

cf. pull request: https://github.com/Nocturnale-Romanum/nocturnale-romanum/pull/228

Broke up the episemata on the first two note of cenTUM