Rename `text` to `lettering`

The function `text :: Text -> Picture` is confusing, because its name suggests that it's describing text, but it's actually describing a picture made from text. I propose we use the word `writing` instead. This is a word whose meaning actually suggests the visual appearance of letters.

Other noun options incluse `print`, `lettering`, or `label`; but they have various issues of their own. There are some adjective options, too, like `written`; but all other primitive picture functions are already named with nouns - and `printed` is already used for the conversion from Number to Text, so that would be confusing.

FYI @alphalambda

Localiza la definición de Haskell y todos los usos de `text :: Text -> Picture`; determina primero qué nombre de reemplazo está aprobado, ya que el título y la propuesta no coinciden. Se considera terminado cuando el sustantivo seleccionado se aplica de forma coherente en todos los lugares donde se expone y se referencia este primitivo.

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