Add svgo-browser link readme

[rtivital]

Привет! Hello, I've made a version of svgo that works in browsers (with help of build tools like webpack). With this pull request I've added link to it.

Link – https://github.com/rtivital/svgo-browse

Here is an API example:

// Test data will be used in all examples to illustrate output
const testData = `
  <svg version="1.1" width="10" height="20">
      test
  </svg>
`;

Optimize with all default configuration:

import optimize from 'svgo-browser/lib/optimize ';

optimize(testData).then(console.log); // -> <svg viewBox="0 0 10 20">test</svg>

Get separate instance:

import getSvgoInstance from 'svgo-browser/lib/get-svgo-instance';

const svgo = getSvgoInstance();
svgo.optimize(testData).then(console.log); // -> { data: "<svg viewBox="0 0 10 20">test</svg>", info: {}}