Add pinning feature to categories

[orzchen]

Clear and concise description of the problem

When there are many subscriptions in a category, I hope there will be a pinning function, so that I can quickly find the important subscriptions no matter how they are sorted. Thanks.

Suggested solution

When you right-click any subscription in the category, the option to pin it to the top will appear.

Alternative

No response

Additional context

No response

Validations

• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.
• This issue is valid

[linear]

FOL-1578 Add pinning feature to categories