Add helper to cache adblocker engine

[remusao]

This PR improves the following methods from adblocker engine/blocker:

• fromLists,
• fromPrebuiltAdsOnly
• fromPrebuiltAdsAndTracking
• fromPrebuiltFull

With an extra argument caching indicating how to cache the resulting engine for faster loading. By default no caching is performed, but if this argument is specified then the engine initialization will:

1. check if engine is already cached, and use this if available (faster)
2. if engine is not cached or loading fails, initializes from scratch (current behavior)
3. new engine is serialized and written to cache for next time.

Example of how to use it with @cliqz/adblocker-puppeteer (API is the same for @cliqz/adblocker-electron and @cliqz/adblocker-webextension):

import puppeteer from 'puppeteer';
import { PuppeteerBlocker } from '@cliqz/adblocker-puppeteer';
import fetch from 'cross-fetch'; // required 'fetch'
import { promises as fs } from 'fs'; // used for caching

const browser = await puppeteer.launch();
const page = await browser.newPage();

PuppeteerBlocker.fromPrebuiltAdsAndTracking(fetch, {
  path: 'engine.bin',
  read: fs.readFile,
  write: fs.writeFile,
}).then((blocker) => {
  blocker.enableBlockingInPage(page);
});