Added dialog tag guide in HTML section (#23173)

guide/english/html/elements/dialog-tag/index.md

@@ -0,0 +1,39 @@
+---
+title: Dialog Tag
+---
+## Dialog Tag
+The `<dialog>` tag defines a dialog box or window.
+
+The `<dialog>` element makes it easy to create popup dialogs and modals on a web page.
+
+The `<dialog>` tag is new in HTML5.
+
+#### Attributes:
+open:
+Indicates that the dialog is active and that the user can interact with it.
+When the open attribute is not set, the dialog shouldn't be shown to the user.
+
+#### Example:
+
+```html
+  <dialog open>
+    <p>This is an open dialog window</p>
+  </dialog>
+```
+
+#### HTML DOM Dialog Object
+
+#### To access a <dialog> element by using getElementById():
+
+  `var dialog = document.getElementById("myDialog");`
+
+####  Create a Dialog Object:
+  `var x = document.createElement("DIALOG");`
+
+#### Dialog Object Methods:
+close() - Closes the dialog<br />
+show() - Shows the dialog<br />
+showModal() - Shows the dialog and makes it the top-most modal dialog
+
+#### Further reading:
+[MDN](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dialog)