[examples][frameworks] Add missing examples and add a test to ensure every framework has an example (#4372)

* Add test to frameworks

* Add example for Docusaurus v2

* Add example for ionic-angular

* Update READMEs

* Use existing versions

* Reset yarn.lock

* Add schema validation and add missing Scully.io logo

examples/ionic-angular/generate-h2-push.js

@@ -0,0 +1,85 @@
+#!/usr/bin/env node
+const puppeteer = require('puppeteer');
+const fs = require('fs');
+const args = process.argv.slice(2);
+const host = args[0] || 'http://127.0.0.1:8080';
+const indexMatches = [
+  '.gz',
+  '.map',
+  '3rdpartylicenses.txt',
+  'ngsw-manifest.json',
+  'ngsw.json',
+  'worker-basic.min.js',
+  'ngsw-worker.js',
+  'favicon',
+  'index.html',
+  'manifest.webmanifest',
+  '.svg'
+];
+let results = '';
+async function main() {
+  const browser = await puppeteer.launch();
+  const page = await browser.newPage();
+  await page._client.send('ServiceWorker.disable')
+
+  page.on('console', msg => console.log(msg.text()));
+
+  console.log('Page: loaded');
+  await page.goto(host);
+
+  const allRequests = new Map();
+  page.on('request', req => {
+    allRequests.set(req.url(), req);
+  });
+
+  await page.reload({ waitUntil: 'networkidle2' });
+
+  Array.from(allRequests.values()).forEach(req => {
+    const url = req.url();
+
+    // filter out urls that match these extensions
+    for (const exlude of indexMatches) {
+      if (url.indexOf(exlude) != -1) return false;
+    }
+
+    // if external, dont worry about it for now
+    //
+    const origin = new URL(host);
+
+    if (url.indexOf(origin.origin) === -1) return false;
+
+    // Format the url to remove the host
+    const formatted = url.replace(`${origin.origin}/`, '');
+
+    if (origin.pathname.includes(formatted)) return false;
+
+    // if it's an empty string, just ignore it
+    if (!formatted) return false;
+
+    let type = url.substr(-3) == 'css' ? 'style' : 'script';
+    results += `</${formatted}>;rel=preload;as=${type},`;
+
+  });
+  await browser.close();
+  updateWith(results);
+}
+function updateWith(result) {
+  fs.readFile('firebase.json', 'utf8', function(err, data) {
+    if (err) {
+      return console.log(err);
+    }
+    let re = /("headers":\s*\[\s*{\s*"key":\s*"Link",\s*"value":\s*")(.*)("\s*}\s*\])/gm;
+    if (re.exec(data)) {
+      let newConfig = data.replace(re, `$1${result}$3`);
+      fs.writeFile('firebase.json', newConfig, 'utf8', function(err) {
+        if (err) return console.log(err);
+        console.log('firebase.json updated successfully.');
+      });
+    } else {
+      console.log("Couldn't find a valid firebase config to update.");
+      return;
+    }
+  });
+}
+
+main();