Enable beat marking

[grotsztaksel]

Particularly useful for a'capella songs with complex lyrics, like:

  <verse>
    Be\fore the \boat had \hit the wa\ter                   | . . . .
    The \whale's \tail came \up and \caught her             | . . . .
    All \hands to the \side, har\pooned and \fought her     | . . . .
    When she \dived \down \below \(Huh!)                    | . . . .
  </verse>

When the notation above is present, the letter preceded with the \ should become bold

[grotsztaksel]

Alternatively, the notation could still use \ to mark, where the chord should be played, while | should mark the beat (like the bar on the staff[^1])

  <verse>
    Be\|fore the |boat had |hit the wa|ter                   | a
    The \|whale's |tail came |up and \|caught her             | d a
    ...
  </verse>

On the other hand, the chord usually goes where the beat should

[^1]: I mean the musical terms, maybe not using them correctly.

[grotsztaksel]

Leave the \ as the marker in the text. When the marker is matched by a chord, place a chord. If it is matched by a period dot ., draw a vertical line | in the text (the same, that is currently used as the default separator between the lyrics and the chords in the XML)

[grotsztaksel]

But a delicate one! Gray for example

<span style="color:#CDCDCD;font-stretch:ultra-condensed">|</span> 
<!-- Though font-stretch has no influence on a single character -->

[grotsztaksel]

Meh. Lousy idea.