+ client: Add a link to the list of known DNS providers to Upstream DNS settings

Closes #734

client/src/__locales/en.json

@@ -259,5 +259,6 @@
     "setup_guide": "Setup guide",
     "dns_addresses": "DNS addresses",
     "down": "Down",
-    "fix": "Fix"
+    "fix": "Fix",
+    "dns_providers": "Here is a <0>list of known DNS providers</0> to choose from."
 }

client/src/components/Settings/Upstream/Examples.js

@@ -4,6 +4,17 @@ import { Trans, withNamespaces } from 'react-i18next';
 
 const Examples = props => (
     <div className="list leading-loose">
+        <p>
+            <Trans
+                components={[
+                    <a href="https://kb.adguard.com/general/dns-providers" target="_blank" rel="noopener noreferrer" key="0">
+                        DNS providers
+                    </a>,
+                ]}
+            >
+                dns_providers
+            </Trans>
+        </p>
         <Trans>examples_title</Trans>:
         <ol className="leading-loose">
             <li>