Mattermost-server: Remove usage of jQuery from theme settings

[mattermod]

We've been working for some time to remove jQuery as a dependency of the Mattermost web app to reduce the size of the JS bundle in the web app and to simplify our code by using equivalent functions that are usable on all browsers that we support.

As part of this, we should remove the usage of jQuery from the following files in the web app:

• components/user_settings/display/user_settings_theme/custom_theme_chooser.jsx
• components/user_settings/display/user_settings_theme/premade_theme_chooser/premade_theme_chooser.jsx
• utils/utils.jsx

In addition to removing the usage of jQuery, E2E tests using Cypress should be added to ensure that:

• Sections properly animate open and closed when editing a custom theme in Account Settings > Display > Theme
• Code themes are properly updated throughout the app when changing them from Account Settings > Display > Theme

If you have any questions, feel free to ask @hmhealey (or @harrison on our Mattermost community server).

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JIRA: https://mattermost.atlassian.net/browse/MM-27446

[jakubnovak998]

Hi, I can work on this.

[hmhealey]

Awesome, thanks! Let us know if you have any questions or anything.

[jfrerich]

This issue appears stale. and I’m adding the Up For Grabs label. If work is ongoing, please remove the label. If there is an existing PR, please also link it to the issue. Thanks!

[lipmem]

I work on it now :)