RewritingStream incorrectly escaping contents of <script> tags via emitText()

[nfriedly]

This is related to but distinct from #333

The RewritingStream.emitText() method always calls escapeString on the text:

parse5/packages/parse5-html-rewriting-stream/lib/index.js

Lines 79 to 81 in 9c683e1

	emitText({ text }) {
	this.push(escapeString(text, false));
	}

This causes it to break JavaScript. For example:

<script type="text/javascript">
(function() {
  if ('PerformanceObserver' in window && 'PerformancePaintTiming' in window) {
    // ...

ends up as

<script type="text/javascript">
(function() {
  if ('PerformanceObserver' in window &amp;&amp; 'PerformancePaintTiming' in window) {
    // ...

and then the browser's JS parser chokes with a syntax error when it hits the &&.

It should probably do something similar to what _serializeTextNode does:

parse5/packages/parse5/lib/serializer/index.js

Lines 136 to 149 in 9c683e1

	if (
	parentTn === $.STYLE ||
	parentTn === $.SCRIPT ||
	parentTn === $.XMP ||
	parentTn === $.IFRAME ||
	parentTn === $.NOEMBED ||
	parentTn === $.NOFRAMES ||
	parentTn === $.PLAINTEXT ||
	parentTn === $.NOSCRIPT
	) {
	this.html += content;
	} else {
	this.html += Serializer.escapeString(content, false);
	}

(Or, whatever it ends up doing after the resolution of #333)

For a short-term workaround, I'm going to just call stream.push() stream.emitRaw() when inside of a <script> tag.