Fix Syosetu and Fanstrans

[NilanEkanayake]

Syosetu has added pages, so I added a check to see if the source has multiple pages, and if so, iterate through them and scrape as normal. (Was a bit of a rush job, technically works but probably has issues)

Also fixed fanstrans on the side.

I locally fixed a couple of other sources too, might commit them later once I've checked them over

[NilanEkanayake]

I added
def initialize(self) -> None: self.init_executor(2)
But it might not be necessary for most. I was downloading a few extremely long (~600 chapter) series, and Syosetu rate limited me.

[dipu-bd]

@NilanEkanayake I have made some quick changes in syosetu. can you please confirm if the changes are okay?

[NilanEkanayake]

Removed duplicate self.novel_url
Tested and verified working!