text-search across linebreaks should normalize whitespace

[Milan Hauth]

example document

```html

some<br>text

```

data:text/html,some<br>text

text-search succeeds to find the query "some

text"

text-search fails to find the query "some text"

expected: matching should be less strict

(whitespace should be normalized)

so that both queries succeed

use case: ebooks in EPUB-FXL format

searching multiple words should work across linebreaks