Height of emoji does not match the height of the text in the same paragraph

[miguelcmedeiros]

While testing #434 I noticed the height of the caret on the right side of an emoji is different than on the rest of the paragraph.
In fact, it seems that the text height for the emoji is taller than rest. The following gif shows the caret height difference and also the text selection behaviour:

[miguelcmedeiros]

Cc @matthew-carroll