reader is changing character count on ttu

[Whitesttax]

I tested this on both firefox and chrome. Used 0.4 release.

Steps to reproduce: (horizontal text, continuous mode, hide furigana on, and style toggle. Doesn't seem to happen for vertical) Open a book, scroll down quite a bit while waiting for the extension to color words, after that copy a sentence just to make sure you can ctrl + f. Bookmark it exactly on the top of the screen to get the exact character count. Check the count. Close the book and open it again. What happens on both browsers is, my bookmark is off, at least a page down, and the character count is less than before. The more you scroll, and therefore use the extension, the more off the character count and bookmark will be. I read that the bookmark uses the character count, so that's why I titled it this way. Tested this several times. I got it off by 5k characters once.

The only thing I noticed is that the extension seems to add a bigger space from when I just open the book/new page and when text gets colored, which could be causing this. Here's an example just in case this is on my end, https://imgur.com/a/b3iShe3

If I disable the extension and repeat the process it works flawlessly, I get the exact same character count as before, and the bookmark is correct as well, so I don't think it's a problem with ttu.