use eslint-config-koa

[hiroppy]

I want to use eslint-config-koa because koajs/koa uses it.

If we use it now, the following error will occur.

semi
arrow-parens
space-before-function-paren
padded-blocks

✖ 169 problems (169 errors, 0 warnings)

@jonathanong What do you think?

[jonathanong]

I don't want to maintain another eslint plugin, better to use an off-the-shelf config like standard