Add QR Code information to markdown (#34981)

* Add QR Code information to markdown

the ha-rq-code tag is undocumented. This should be added

* Update markdown.markdown

typos corrected

* Apply suggestions from code review

* Apply suggestions from code review

---------

Co-authored-by: c0ffeeca7 <38767475+c0ffeeca7@users.noreply.github.com>

source/_dashboards/markdown.markdown

@@ -150,3 +150,28 @@ content: |
   <ha-alert alert-type="success">This is a success alert — check it out!</ha-alert>
   <ha-alert title="Test alert">This is an alert with a title</ha-alert>
 ```
+
+## ha-qr-code
+
+You can also create QR-Codes in the Markdown card.
+
+Available parameters:
+- data: The actual data to encode in the QR-Code
+- scale: A scale factor for the QR code, default is 4
+- width: Width of the QR code in pixels
+- margin: A margin around the QR code
+- error-correction-level: low; medium; quartile; high)
+- center-image: An image to place on top of the qr code (might need a higher error-correction-level)
+
+```yaml
+type: markdown
+content: >-
+  <ha-qr-code data='hallo' width="180"></ha-qr-code>
+
+  <ha-qr-code data='hallo' scale="6" margin="0"
+  center-image="/static/icons/favicon-192x192.png"></ha-qr-code>
+
+  <ha-qr-code data='hallo' error-correction-level="quartile" scale="6"
+  center-image="https://brands.home-assistant.io/_/tuya/icon@2x.png"></ha-qr-code>
+```
+