feat: add uninstall button to store

[alvaro-cuesta]

Please tick as appropriate:

• [x] I have tested this code on a steam deck or on a PC
• [x] My changes generate no new errors/warnings
• [ ] This is a bugfix/hotfix
• [x] This is a new feature

Description

This is a followup to PR #733. After discussing with @TrainDoctor on Discord he suggested it would be a good idea to also add an uninstall button to the store next to the "Reinstall" button (to plugins which are already installed).

To make the functionality more obvious, the button will only be shown on the "Reinstall" case, i.e. when the currently installed version is selected in the dropdown.

[TrainDoctor]

@AAGaming00 need you to confirm any questions PR submitter had to make sure there aren't any issues with frontend changes made. Once the frontend changes have been reviewed I'll give this a spin myself.

[AAGaming00]

@alvaro-cuesta please revert 48f23f the class names are there intentionally to aid theme devs

we should really document this practice...