Add sub restriction info on Steam store page subs (for gifting)

[enchained]

Is your feature request related to a problem? Please describe.

I was thinking about how to make cross-region gifting process easier (more thoughts on it here: IsThereAnyDeal/AugmentedSteam#2098)

SteamDB already stores info about "This package can NOT be activated or purchased in the following countries". It would be really great if SteamDB extension could:

• Show "has restrictions" icon next to the sub on steam storefront pages
• Show "Not in AB CD EF" tooltip on hover
• If the list is too long (like with Sony titles), clickable popup could be used

Notes:

• I noticed that "No cross region trading and gifting" box does not have the intended impact for some reason, at least in my experience. A lot of times the game is still giftable with it, only "This package can NOT be activated or purchased in the following countries" caused errors (other than simple 10%+ price difference errors).
• Other than Sony case it could be useful for older games with many regional storefront subs, and also with some new games with restrictions in some regions.
• I also noticed when games got restricted in Germany recently, it was used via the app key "restricted_countries". I am not sure whether it also affects gifting and should be accounted for.

Describe the solution you'd like

No response

Describe alternatives you've considered

No response