Adds note about `Text` class for developers interested in extensions. (fixed typo)
Adds note about `Text` class for developers interested in extensions. (fixed typo)

kzykhys/Ciconia,scribenet/jabiru,fluxbb/commonmark,scribenet/Scrible,simonfork/Ciconia,gharlan/Ciconia,scribenet/Scrible,scribenet/jabiru