Feat: Add background color change on hover to nav links

[NihadBadalov]

⚠️⚠️⚠️ Since we do not accept all types of pull requests and do not want to waste your time. Please be sure that you have read pull request rules:
https://github.com/louislam/uptime-kuma/blob/master/CONTRIBUTING.md#can-i-create-a-pull-request-for-uptime-kuma

Tick the checkbox if you understand [x]:

• I have read and understand the pull request rules.

Description

Fixes #1753

Type of change

Please delete any options that are not relevant.

• User interface (UI)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas (including JSDoc for methods)
• My changes generates no new warnings
• My code needed automated testing. I have added them (this is optional task)

Screenshots (if any)

Theme	hovering over selected	hovering over non-selected
dark
light

[CommanderStorm]

This does not really look like the other button-hover effects we already have.
I see why you thought that this would be the correct approach. The item-hoverable things, such as single status pages, behave this way.
I think currently these are buttons (maybe they should not? => unclear)

=> making this primary on hover not truly fit into the current design language as far as I see. (open to discussion)

I would expect this to be a light-gray in the light mode and a dark gray in the dark mode, as the other buttons "lighten" on hover.

[CommanderStorm]

I have tested this PR and the current way this is implemented is not mergable. I have updated the screenshots in the description.

Again, my communication was not clear in the review. Need to work on that ^^

In the dark mode the currently selected button is now just black on dark gray if hovered over, and in the light mode it does not have any visual effect I can perceive.
I would expect this to behave like our other buttons…

The hover effect for non-selected looks nice though 👍🏻