Add support for the Random Battle format

https://randbatscalc.github.io/

• Add a format selector (Standard vs. Random, later VGC and BSS etc) along with the generation and mode selectors
• This mode should likely implemented as a separate page from index.template.html
• This mode can include information about the ‘pools’ available (Ability/Move/Damaging move pool)

@LegoFigure11

[scheibo]

My plan here is currently to repurpose the actual random-teams.js code from PS to generate the correct pools of abilities/items/moves. The new UI will only be slightly different for random formats - the moves in the move pool will be sorted to the top of the select box (in the same way high usage moves are sorted to the top of the select box for non random formats), and there will be a divider line or some other visual distinction to separate which moves are part of the pool or not.

This will result in slightly more clicks to select moves in the pool than the randbats calc UI, but harmonizes it with the other formats. I’m open to revisiting the UI to make it more like the randbats calc (with buttons to quickly toggle through selections in the pool), but I’d like to try the simpler UI to begin with.

[scheibo]

@AustinXII please see the initial comment here (ie. randoms should be a separate page in the current UI most likely).

As I mentioned, I’ve abandoned the idea of generating pools as I was doing above because its slightly intractable given how the random battle generators change often. @TheImmortal suggested usage stats, I’m going to process the latest random battle usage stats from January into the information we need and commit the data files (today or tomorrow) so that you have something to work with. Until https://github.com/pkmn/stats ships and makes processing more efficient such that we can always get random battle stats we can run randombattle stats on demand with the current processing logic as needed