Add documentation for IRequestHeader (#20673)

## Description

[Task:
](https://dev.azure.com/fluidframework/internal/_workitems/edit/7164)
Adding documentation for IRequestheader.

---------

Co-authored-by: Jatin Garg <jatingarg@Jatins-MacBook-Pro-2.local>

Author: jatgarg

packages/common/driver-definitions/src/urlResolver.ts

@@ -93,7 +93,11 @@ export interface IDriverHeader {
 }
 
 declare module "@fluidframework/core-interfaces" {
-	// TODO: This interface should be documented. AB#7164
-	// eslint-disable-next-line @typescript-eslint/no-empty-interface, jsdoc/require-jsdoc
+	/**
+	 * Interface to represent headers to include in the container or data store load request.
+	 * For example, caller can use this to pass on various loader options in the container
+	 * load request.
+	 */
+	// eslint-disable-next-line @typescript-eslint/no-empty-interface
 	export interface IRequestHeader extends Partial<IDriverHeader> {}
 }