Refactor Web Extensions Permissions API examples to async/await

[Hamatti]

Description

Refactoring the examples in Web Extensions Permissions API from .then() syntax to async/await syntax.

Motivation

We are moving towards having the Web Extensions examples using that syntax and as I'm writing a blog post for the add-ons community blog where I use these examples, it came up that this would be a good moment to refactor them in MDN and then use the same format in the blog post.

For example, tabs API and background_scripts are already refactored.

Additional details

Related issues and pull requests

[github-actions[bot]]

Preview URLs

• /en-US/docs/Mozilla/Add-ons/WebExtensions/API/permissions/contains
• /en-US/docs/Mozilla/Add-ons/WebExtensions/API/permissions/getAll
• /en-US/docs/Mozilla/Add-ons/WebExtensions/API/permissions/remove
• /en-US/docs/Mozilla/Add-ons/WebExtensions/API/permissions/request

(this comment was updated 2022-11-07 12:56:48.569094)

[bsmth]

Thanks @Hamatti and @rebloor, merging 🙌🏻