Pull request: 3115 domain case

Merge in DNS/adguard-home from 3115-domain-case to master

Updates #3115.

Squashed commit of the following:

commit 02b6d27d862b3e3dc2a17220cec35f0f18e31fb3
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue May 11 19:56:06 2021 +0300

    all: fix typos

commit cdd1de64d5f79605b5fdcad5879204194856b083
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue May 11 19:37:37 2021 +0300

    dnsforward: fix disallowed domains case matching

internal/dnsforward/access.go

@@ -47,7 +47,7 @@ func newAccessCtx(allowedClients, disallowedClients, blockedHosts []string) (a *
 
 	b := &strings.Builder{}
 	for _, s := range blockedHosts {
-		aghstrings.WriteToBuilder(b, s, "\n")
+		aghstrings.WriteToBuilder(b, strings.ToLower(s), "\n")
 	}
 
 	listArray := []filterlist.RuleList{}