state the default for a attribute (#22460)

state the default for the `form` element's `method` attribute

files/en-us/web/html/element/form/index.md

@@ -148,7 +148,7 @@ The following attributes control behavior during form submission.
     The only allowed methods/values are (case insensitive):
 
     - `post`: The [POST method](https://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.5); form data sent as the [request body](/en-US/docs/Web/API/Request/body).
-    - `get`: The [GET method](https://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.3); form data appended to the `action` URL with a `?` separator. Use this method when the form [has no side effects](/en-US/docs/Glossary/Idempotent).
+    - `get` (default): The [GET method](https://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.3); form data appended to the `action` URL with a `?` separator. Use this method when the form [has no side effects](/en-US/docs/Glossary/Idempotent).
     - `dialog`: When the form is inside a {{HTMLElement("dialog")}}, closes the dialog and throws a submit event on submission without submitting data or clearing the form.
 
     This value is overridden by {{htmlattrxref("formmethod", "button")}} attributes on {{HTMLElement("button")}}, [`<input type="submit">`](/en-US/docs/Web/HTML/Element/input/submit), or [`<input type="image">`](/en-US/docs/Web/HTML/Element/input/image) elements.