rrdom (#613)

* create rrdom package

* test(rrdom): add unit tests for polyfill.ts

* fix(rrweb snapshot): type check errors

Errors are caused by the declaration similarity of @types/mocha and @types/jest if we install both of them in the whole project.

* Set tagNames to upper case by default

This mirrors the `Element.tagName` implementation:

```
For DOM trees which represent HTML documents, the returned tag name is always in the canonical upper-case form. For example, tagName called on a <div> element returns "DIV".
```
https://developer.mozilla.org/en-US/docs/Web/API/Element/tagName

* Add workspace file

* VSCode settings for rrdom tests

* Add basic test for RRDocument

* Only setup jest tests for rrdom

* mock Node type and Event type for nodejs environment

* test(rrdom): add snapshot for document.test.ts

* fix issue of nwsapi import and add unit tests for rrdom

* fix: querySelectorAll returns nothing when querying elements with ids and classNames

* fix: error of unit test for Event polyfill

Since Event class is built in nodejs after v15.0.0

* add a dummy implementation of canvas

* add style element support

* add unit test for style element

Co-authored-by: Justin Halsall <Juice10@users.noreply.github.com>

packages/rrdom/test/util.ts

@@ -0,0 +1,19 @@
+import { RRIframeElement, RRNode } from '../src/document-nodejs';
+
+/**
+ * Print the RRDom as a string.
+ * @param rootNode the root node of the RRDom tree
+ * @returns printed string
+ */
+export function printRRDom(rootNode: RRNode) {
+  return walk(rootNode, '');
+}
+
+function walk(node: RRNode, blankSpace: string) {
+  let printText = `${blankSpace}${node.toString()}\n`;
+  for (const child of node.childNodes)
+    printText += walk(child, blankSpace + '  ');
+  if (node instanceof RRIframeElement)
+    printText += walk(node.contentDocument, blankSpace + '  ');
+  return printText;
+}