Added "Axiom" and "Assumption" theorem environments and spanish translations for them.

[SrShelo]

First of all, let me know if anything sounds confusing since English is not my native language.

Description

Have been added:

• axioms and assumptions (abreviated 'axn' and 'asp' respectively) with definition style in a table which defines theorem evironments (src/resources/filters/customnodes/theorem.lua).
• the corresponding entries to _language.yml and _language-es.yml (translated by me, a native spanish speaker and math student).
  This works fine with documents in english, but in spanish Quarto seems to not read correctly _language-es.yml. Maybe it is necessary to add definitions somewhere. Intervention might be required.
  Anyways, the translation is already done for spanish.
  With these 2 new theorem types I think it is enough for default theorem environments.

#3979

Checklist

I have (if applicable):

• filed a contributor agreement.
• referenced the GitHub issue this PR closes
• updated the appropriate changelog in the PR
• ensured the present test suite passes
• added new tests
• created a separate documentation PR in Quarto's website repo and linked it to this PR

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