Typo in element_text docs

[concimuscb]

Currently element_text() docs state that the size is defined in pt. However, upon testing, it appears to be in px instead.

My rudimentary testing was as follows:

• Create chart and export to svg
• Import chart into PPT and compare with text with the same settings than in Lets-Plot

When I set the text size in pt, the text does not line up with the one from power point. If I set up the size in LetsPlot assuming that it is px instead, then the text in the output chart has exactly the same size as the one in powerpoint.