Replace Boilerpipe functionality with more modern Readability clone

[mjsuhonos]

Problem
Class ExtractBoilerpipeText doesn't fully do what it purports to; ie. it sometimes leaves (often large) portions of eg. header and comment thread text in the output. Boilerpipe was last updated 10 years ago.

Preferred solution
Boilerplate removal more consistent with Readability.js, based on a more modern Java/Scala library.

Alternatives considered
There are two libraries available:

• Readability4J: more recent, more active
• readability4s: pure Scala, but moribund

Additional context
Advice on selecting a library would be much appreciated; I suspect the main consideration will be maintainability.

I'm happy to write up a test and PR for this issue once there's a decision. I can provide failing examples if that's helpful.

[ruebot]

Very much agree that Boilerpipe should be replaced. I can't say that I haven't thought about it over the years 😅

Both libraries you link to look promising, but also seem to be slightly less moribund than Boilerpipe. Curious if there will be an comment on this issue.

If you want to take a crack at replacing Boilerpipe with Readability4J, I'd be happy to take a look at it or give you a hand. Also, happy to look around and see if there are any other options than these two that have more activity. Let me know what you think.