docs: update custom http headers kb

[petar-i-todorov]

Partially addresses https://github.com/telerik/reporting/issues/4645.

Also makes the article generic for all HTML5-based report viewers, and addresses the usage of the fetch API in the latest release.

[Copilot]

Pull Request Overview

This PR refactors the KB article to be generic for all HTML5-based report viewers and adds guidance on using the browser’s Fetch API for header injection in the latest release.

• Generalized title, slug, and page metadata for HTML5-based viewers.
• Added a list of supported viewers and unified the description.
• Introduced two solutions: native authenticationToken option and overriding fetch() for versions ≥ 19.1.25.521, plus the legacy jQuery approach.

Comments suppressed due to low confidence (3)

knowledge-base/custom-headers-with-reportviewer-rest-api-calls.md:56

• The code fence uses four backticks and is labeled 'JavaScript' but the snippet includes TypeScript-specific syntax. Consider switching to a triple backtick fence with 'TypeScript' or removing type annotations for consistency.

		````JavaScript

knowledge-base/custom-headers-with-reportviewer-rest-api-calls.md:59

• The override function signature includes TypeScript types (e.g., RequestInfo | URL), but the fence is labeled JavaScript. Use a TypeScript fence or remove types to avoid confusion.

			window.fetch = async function (

knowledge-base/custom-headers-with-reportviewer-rest-api-calls.md:91

• [nitpick] The block quote uses '>note' without a space and lowercase 'note'. Standard markdown admonitions typically use '> Note:' with a space and capital letter for readability.

	>note In both cases, ensure that this JavaScript is executed before the report viewer is initialized, so that the overridden fetch logic takes effect during the initialization process.

[dnikolov-prg]

Looks good