* extend library search to enable -<source> search
library search already allows for <source> search to select manga from a
particular source. Similarly, -<source> allows to search for manga that
aren't from the said source. TachiyomiSy has this feature but it heavily
depends on exh methods
A problem when you directly add a negation check is that although
it will work, the genre search kicks in adds back every manga since
-<source> returns true for all genres of a manga
Thus, the solution I decided on was do source search first, and then
move to genre check when it fails. A perhaps useful addition is that,
now you're able to search like this:
<genre1>, -<source>, -<genre2>
* make if-else statements more readable
* refactor containsSourceOrGenre() using `when`
* add comment describing the function
* remove lazy
not really required anymore now that containsSourceOrGenre was rewritten
using `when`