Add documentation for Playwright helpers

[anagstef]

⚠️ We first need to release this: clerk/javascript#4006

Important

🔎 Previews:

• https://clerk.com/docs/pr/1529/testing/playwright

This PR:

• Adds documentation for helper functions in the Playwright integration of the @clerk/testing package.

[github-actions]

Hey, here’s your docs preview: https://clerk.com/docs/pr/1529

[LekoArts]

Removing "just do X" to not make feel people who struggle with the instructions after it

Suggested change

	To use these commands, you just have to import the `clerk` object from the `@clerk/testing/playwright` package.
	To use these commands, import the `clerk` object from the `@clerk/testing/playwright` package.

[LekoArts]

Suggested change

	The `clerk.signIn` function is used to sign in a user using Clerk. This helper supports only the following first factor strategies:
	The `clerk.signIn()` function is used to sign in a user using Clerk. This helper supports only the following first factor strategies:

[LekoArts]

Suggested change

	> This helper function internally uses the `setupClerkTestingToken()` helper, so you don't need to call it separately.
	> `clerk.signIn()` internally uses the `setupClerkTestingToken()` helper, so you don't need to call it separately.

To not repeat "helper"

[LekoArts]

Suggested change

	- Before calling this function, you must call `page.goto`.
	- Before using this function, navigate to a non-protected page that loads Clerk.
	- Navigate to a non-protected page that loads Clerk via `page.goto()`, for example the index page

[LekoArts]

Suggested change

	`clerk.signIn` accepts an object with the following properties:
	`clerk.signIn()` accepts an object with the following properties:

[LekoArts]

Suggested change

	The following example demonstrates how to use the `clerk.signOut` helper in a test to sign a user out.
	The following example demonstrates how to use `clerk.signOut()` in a test to sign out a user.

[LekoArts]

Suggested change

	The `clerk.loaded` function asserts that Clerk has been loaded.
	`clerk.loaded()` asserts that Clerk has been loaded.

[LekoArts]

Suggested change

	- Before calling this command, you must call `page.goto`.
	- Before using this command, navigate to a page that loads Clerk.
	- Navigate to a non-protected page that loads Clerk via `page.goto()`, for example the index page

[LekoArts]

Suggested change

	`clerk.loaded` accepts an object with the following properties:
	`clerk.loaded()` accepts an object with the following properties:

[LekoArts]

Suggested change

	The following example demonstrates how to use the `clerk.loaded` helper in a test to assert that Clerk has been loaded.
	The following example demonstrates how to use `clerk.loaded()` in a test to assert that Clerk has been loaded.