Improve action bar on posts

[winston-yallow]

This introduces the following changes:

• background on hover is rounded
• mark as solved and like buttons use green font
• background on solved and like buttons is green on hover

Default View

Hovered Buttons

With Like Count

Fixes #4
Fixes #7

[akien-mga]

I don't speak CSS fluently, but the screenshots look good to me :)

[winston-yallow]

Forgot the state of a post being liked by you already, fixed it now. Thumb is green in this case too but filled.

[akien-mga]

Overall, it seems to me like the accent color is red and used for everything. E.g.:

We might end up playing whack-a-mole with this if we want to override it only for positively charged symbols.

Maybe we should change the accent to Godot blue?

[winston-yallow]

I'll see how it looks with Godot blue, would make sense to change it.

But that's unrelated to making these two buttons green, I think that's still preferred over the default accent color whatever it is. Also the like button uses the "love" color since in Discourse it originally is a heart, so even changing the default accent color would not solve #7.

[winston-yallow]

Will merge during Planned Maintenance