Height estimation is incorrect for a majority of custom fonts

[iGerman00]

In the screenshot I've loaded Source Sans Pro on the right which works correctly and is perfectly centered,
I also loaded in a random TTF font from dafont, and it's not centered. This is the case for most custom fonts I load, especially the artsy ones.

Changing the baseline, unfortunately, doesn't help much, with ideographic being the closest to being centered, and the rest just putting it even lower

[iGerman00]

I've just updated to 4.1.1 (sorry about that and the last issue), and it seems like now it also completely ignores the context textBaseline? The issue otherwise is still present

[stefcameron]

I wonder if this is because of the way the library currently calculates the height of the text by setting the baseline to 'bottom' and use the TextMetrics.actualBoundingBoxAscent as the height, instead of using the newer TextMetrics.fontBoundingBoxAscent + TextMetrics.fontBoundingBoxDescent, which I believe consider the height of entire font instead of exactly what's rendered (so you get a bit more buffer).

In #95, I propose to move the library to use those newer metrics if available (note that the Node-based canvas package for rendering to canvas in Node does not support these, so the library falls back to its old calculation if that's the case).

[iGerman00]

I noticed that there was a new package released by a third party as a result. I'm not sure if it actually fixed the issue since I can't change the font in their demo, but if it has, would you be able to look into adding it into this package?

[iGerman00]

@geongeorge Bumping this since an update to my software is coming soon. If you could take a look at both the non-functional baseline config and the line height estimation, I'd really appreciate it.