Migration typescript/channel sidebar.js (#25812)

* refactor: convert channel_sidebar.js to ts

- convert file to typescript

* refactor: add type for category on channel_sidebar.ts

- create interface Category into channel_sidebar.ts
- remove file with type category.d.ts

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

e2e-tests/cypress/tests/integration/channels/channel_sidebar/category.d.ts

@@ -1,44 +0,0 @@
-// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
-// See LICENSE.txt for license information.
-
-/// <reference types="cypress" />
-
-// ***************************************************************
-// Each command should be properly documented using JSDoc.
-// See https://jsdoc.app/index.html for reference.
-// Basic requirements for documentation are the following:
-// - Meaningful description
-// - Each parameter with `@params`
-// - Return value with `@returns`
-// - Example usage with `@example`
-// Custom command should follow naming convention of having `ui` prefix, e.g. `uiOpenFilePreviewModal`.
-// ***************************************************************
-
-declare namespace Cypress {
-    interface Chainable {
-
-        /**
-         * Create a new category
-         *
-         * @param [categoryName] category's name
-         *
-         * @example
-         *   cy.uiCreateSidebarCategory();
-         */
-        uiCreateSidebarCategory(categoryName?: string): Chainable;
-
-        /**
-         * Move a channel to a category.
-         * Open the channel menu, select Move to, and click either New Category or on the category.
-         *
-         * @param channelName channel's name
-         * @param categoryName category's name
-         * @param [newCategory=false] create a new category to move into
-         * @param [isChannelId=false] whether channelName is a channel ID
-         *
-         * @example
-         *   cy.uiMoveChannelToCategory('Town Square', 'Favorites');
-         */
-        uiMoveChannelToCategory(channelName: string, categoryName: string, newCategory: boolean = false, isChannelId: boolean = false): Chainable;
-    }
-}