docs: clarify setContent semantics (#24553)

Fixes https://github.com/microsoft/playwright/issues/24503

docs/src/api/class-frame.md

@@ -1610,6 +1610,8 @@ When all steps combined have not finished during the specified [`option: timeout
 ## async method: Frame.setContent
 * since: v1.8
 
+This method internally calls [document.write()](https://developer.mozilla.org/en-US/docs/Web/API/Document/write), inheriting all its specific characteristics and behaviors.
+
 ### param: Frame.setContent.html
 * since: v1.8
 - `html` <[string]>

docs/src/api/class-page.md

@@ -3531,6 +3531,8 @@ When all steps combined have not finished during the specified [`option: timeout
 ## async method: Page.setContent
 * since: v1.8
 
+This method internally calls [document.write()](https://developer.mozilla.org/en-US/docs/Web/API/Document/write), inheriting all its specific characteristics and behaviors.
+
 ### param: Page.setContent.html
 * since: v1.8
 - `html` <[string]>

packages/playwright-core/types/types.d.ts

@@ -3815,6 +3815,8 @@ export interface Page {
   }): Promise<void>;
 
   /**
+   * This method internally calls [document.write()](https://developer.mozilla.org/en-US/docs/Web/API/Document/write),
+   * inheriting all its specific characteristics and behaviors.
    * @param html HTML markup to assign to the page.
    * @param options
    */
@@ -6900,6 +6902,8 @@ export interface Frame {
   }): Promise<void>;
 
   /**
+   * This method internally calls [document.write()](https://developer.mozilla.org/en-US/docs/Web/API/Document/write),
+   * inheriting all its specific characteristics and behaviors.
    * @param html HTML markup to assign to the page.
    * @param options
    */