Adds Webtoons (https://www.webtoons.com) as a metadata provider. Needs some touching up, but I wanted to get revisions/comments in.

Notes and stuffs:

• I've treated each webtoon chapter as a komf book since that's how Kavita and Komga will treat the dowloaded .cbzs, and it allows downloading the chapter images to have proper "covers".
• Linking to cover images for the komf userscript doesn't work since the request sends a referrer that the website blocks. (Of the mediaserver instead of the webtoon page).
• For testing I needed to do a small patch, since Webtoons very commonly separate by "chapter" rather than "volume", to BookNameParser.kt. WEBTOON could perhaps be its own content category?

-    fun getBookNumber(name: String) = getBookNumber(name, bookNumberRegexes)
+    fun getBookNumber(name: String) = getBookNumber(name, bookNumberRegexes) ?: getChapters(name)

• There's probably some more metadata mapping that could be done that I've missed
  • Most notably, the publishing status, but that's not easily discoverable from what I could tell
• The source is currently hardcoded to use the english page for simplicity, though it can be "generalised" easily enough
• I'd really like to figure out grabbing all the chapters like the mobile client does before merging, because otherwise "finished" series only have a few chapters to go off Not considering due to potential DMCA complains about reverse engineering APIs
• Author and other roles parsing was done as best-effort, though it may get some values mixed up due to the many varying layouts

Based partly on keiyoushi's Mihon extension.