Koa Decoded Querystring

To use

``js
const koaDecodedQuerystring = require('koa-decoded-querystring');
// ...
app.use(koaDecodedQuerystring());
`

Very Simple

This module is 5 lines long

`js
// call function to allow for future options as advised by koa best-practices
module.exports = () =>
(ctx, next) => {
ctx.decodedQuerystring = decodeURIComponent(ctx.querystring);
return next();
};
``

So when ctx.querystring contains "%20", decodedQuerystring will contain a
space instead

I only created this module to isolate the testing and any further additions.