* Polish some grammar in places.
* Correct some capitalization nitpicks.
* Use "newline" rather than "line feed", which tends to be more common
in Kakoune's documentation thusfar.
I rephrased some sections, as some of them read a little odd.
* Zero width assertions
* Consistently use "subject's beginning" instead of "subject begin",
it reads better.
* Improve the flow of the word boundary descriptions.
* Modifiers
* Improve phrasing to emphasize the linear nature of their usage and
remove a double negative.
* Use `.` instead of "dot", since that aids in searching through the
page for things talking about the dot character.
* Compatibility
* Use asciidoc syntax for the link to the ECMA-262 standard.
* Use better punctuation on the point about escapes.
