[whatwg] Foreign fallback appcache entries

[Alexey Proskuryakov]

In definitions of application cache entry categories, it's mentioned that an explicit entry can also be marked as foreign. This contrasts with fallback entries, for which no such notice is made.

It still appears that the intention was for fallback entries to sometimes be foreign - in particular, section 6.5.1 says "Let candidate be the fallback resource" and then "If candidate is not marked as foreign..."

I found it confusing that there is a specific mention of foreign for explicit entries, but not for fallback ones.

- WBR, Alexey Proskuryakov