Add ProtonDB button

[peterfour]

Added the ProtonDB button next to the PCGamingWiki.
I find myself wanting to go from the store directly to the protondb website to see how the game run on linux.

I find that it makes it a lot easier

[peterfour]

Just realised the README image might need updating as well.
Let me know if the image should be changed as well to include the proton db button @xPaw

[ejenk0]

I also think an optional line indicating a product's status on protondb (borked, bronze, silver, gold, platinum) along with the corresponding badge would be really useful. For example right here:

[peterfour]

Don't know if that would make sense to include data unrelated to SteamDB in a steamdb extension, that's why I limited the pr to only showing a button since it was already doing it for PCGaming wiki, but we'll see

[krmckone]

I haven't looked to see in depth how extensive there's configuration options for various things like that but maybe it's worth a checkbox to hide/show protondb status in addition to the direct link?

[xPaw]

As I've said before, there's already a protondb extension which shows the actual status, not just a link. Why not work with that?

[peterfour]

As I've said before, there's already a protondb extension which shows the actual status, not just a link. Why not work with that?

Hum that's true, my way of seeing it was that having the button would be handy when I do need it, but the rest of the time keeping the page simple. I don't necessarily need to see the proton rating everytime, just a quick way to get to the page if I want to check it.
Same with the pcgamingwiki, we could potentially also have the data for ultrawide, high fps etc, but the button is enough for punctual checks