Add a 'Battle Rules' article for EBC

[scheibo]

Can't verify with testing. FWIW, the following assumptions should probably be fixed with respect to the build.

• the assumption Zarel/Pokemon-Showdown-Client exists at ../play.pokemonshowdown.com
• there is no package.json listing a dependency on the required showdown package
• the build dies if .articles-cached/ doesn't exist instead of making the directory
• turning line breaks used to wrap long lines into hard <br /> tags is pretty obnoxious

Even after getting the build to work, I couldn't figure out how to get 'Rules' article to load in the test client (I could get 'Critical Hit' to load though), but I verified the it look sane by manually opening the built file:

I will comment with the link in config/ruleset.js on the server once this lands.

[Zarel]

Oh yeah heh I never really expended much effort into making this easy to build.

The linebreak-to-<br /> conversion is intentional, though. GFM is also like that. Too many casual users pressing Enter and producing text that looks fine to them but awful when linebreaks are collapsed.

[Zarel]

I think the name "Rules" is probably too generic. Maybe something like "Battle Rules"?

[scheibo]

I think the name "Rules" is probably too generic. Maybe something like "Battle Rules"?

Done.