Fix mixed text direction

HTML5 addresses another need: text dropped into a page, say from a database, when you don't know its base direction. Before HTML5, you could only set the dir attribute to ltr or rtl, and had to somehow determine yourself which of them was appropriate.

HTML5 provides a new value for the dir attribute: auto. The auto value tells the browser to look at the first strongly typed character in the element. If it's a right-to-left typed character such as a Hebrew or Arabic letter, the element will get a direction of rtl. If it's, say, a Latin character, the direction will be ltr.

There are corner cases where this may not give the desired outcome, but it should usually produce the desired result.

Note that the browser ignores any neutral or weak characters at the beginning of the text when looking for the first strong character. It also ignores anything inside a bdi element or an element with a dir tag of its own, including auto.

Like any other use of the dir attribute in HTML5, dir="auto" also directionally isolates its content from its surroundings.