I love the simplicity of microbundle, but I need to do a bit more than what the default configuration it builds up provides.

More specifically, I want to be able to import SVG images.
Issue #679 says "for that we recommend going with rollup directly and writing a config for your needs.".

Given everything microbundle does for me, having to let it go and configure rollup myself just because of some SVG files makes me quite sad, so I pulled up this PoC of how microbundle could allow some customization of its build config.

@marvinhagemeister as you were the one making that statement in the SVG issue, maybe you'd be able to review/comment this?

It's quite "quick and dirty" for the moment, but I first wanted to know whether that could be a direction microbundle could take?

As a concrete example, that PR allows me to add a microbundle.config.js file into my project and support importing SVG files by importing the @rollup/plugin-image plugin:

const image = require('@rollup/plugin-image')

module.exports = {
  plugins: {
    typescript: function (config) {
      // Since imported *.svg will be transformed to ES modules by the image plugin, tell
      // TypeScript to process them
      return { ...config, include: ['*.ts+(|x)', '**/*.ts+(|x)', '*.svg', '**/*.svg'] }
    },
  },

  config: function (config) {
    // Add image plugin right after json plugin
    const jsonIdx = config.inputOptions.plugins.findIndex((p) => p.name === 'json')
    config.inputOptions.plugins.splice(jsonIdx + 1, 0, image())
    return config
  },
}