Feature request: add an allowed bibliographic keyword

[benjub]

As MM> HELP WRITE BIBLIOGRAPHY indicates,

The <keyword>, which is not case-sensitive, must be one of the following:

    Axiom, Chapter, Claim, Compare, Conclusion, Condition, Conjecture,
    Corollary, Definition, Equation, Example, Exercise, Fact, Figure,
    Introduction, Item, Lemma, Lemmas, Line, Lines, Notation, Note,
    Observation, Paragraph, Part, Postulate, Problem, Proof, Property,
    Proposition, Remark, Result, Rule, Scheme, Scolia, Scolion, Section,
    Statement, Subsection, Table, Theorem

Can we add the allowed keyword Criterion which sometimes comes up in textbooks ? (I have a specific example from Bourbaki (for ~ishmeo) that I'd like to cite correctly in a comment.)