Add cross references from translations

[KallynGowdy]

The API would benefit greatly from having cross-reference data from translations. USX has a spec for cross-reference notes, which some translations (like the BSB) utilize. When parsed, they should produce JSON that looks somewhat like this:

interface ChapterData {
    // ...
    
   /**
    * The list of cross-references for the chapter.
    */
   references: ChapterCrossReference[];
}

interface ChapterVerse {
    // ...
    /**
     * The list of content for the verse.
     * Each element in the list could be a string, formatted text, or a footnote reference.
     */
    content: (
        | string
        | FormattedText
        | InlineHeading
        | InlineLineBreak
        | VerseFootnoteReference
        | VerseCrossReference
    )[];
}

interface VerseCrossReference {
    refId: number;
}

interface ChapterCrossReference {
    refId: number;
    source?: VerseRef;
    references: VerseRef[];
}