For example when the cursor is _on_ the `'` in `'word'`, the cursor
wouldn't move because the search for a matching pair started _from_ the
position of the cursor and simply found itself.
* Add textobjects for word
* Add textobjects for surround characters
* Apply clippy lints
* Remove ThisWordPrevBound in favor of PrevWordEnd
It's the same as PrevWordEnd except for taking the current char
into account, so use a "flag" to capture that usecase
* Add tests for PrevWordEnd movement
* Remove ThisWord* movements
They did not preserve anchor positions and were only used
for textobject boundary search anyway so replace them with
simple position finding functions
* Rewrite tests of word textobject
* Add tests for surround textobject
* Add textobject docs
* Refactor textobject word position functions
* Apply clippy lints on textobject
* Fix overflow error with textobjects
