Pull request: 2843 upd dnsproxy

Merge in DNS/adguard-home from 2843-upd-dnsproxy to master

Closes #2843.

Squashed commit of the following:

commit c3ffddcbf85cbd2542c5bb111984a8f422113a24
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue Apr 20 19:39:11 2021 +0300

    all: fix docs

commit 4b596e4776bfc05e4171bc53e8f9c55c88e1e6a5
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue Apr 20 19:25:24 2021 +0300

    all: imp code, docs

commit 8e3655f4f888ccc2c0902373cf8dd2aa4e113857
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue Apr 20 18:41:14 2021 +0300

    all: upd dnsproxy

CHANGELOG.md

@@ -33,6 +33,8 @@ and this project adheres to
 
 ### Changed
 
+- Our DoQ implementation is now updated to conform to the latest standard
+  [draft][doq-draft-02] ([#2843]).
 - Quality of logging ([#2954]).
 - Normalization of hostnames sent by DHCP clients ([#2945], [#2952]).
 - The access to the private hosts is now forbidden for users from external
@@ -78,6 +80,7 @@ and this project adheres to
 [#2828]: https://github.com/AdguardTeam/AdGuardHome/issues/2828
 [#2835]: https://github.com/AdguardTeam/AdGuardHome/issues/2835
 [#2838]: https://github.com/AdguardTeam/AdGuardHome/issues/2838
+[#2843]: https://github.com/AdguardTeam/AdGuardHome/issues/2843
 [#2889]: https://github.com/AdguardTeam/AdGuardHome/issues/2889
 [#2927]: https://github.com/AdguardTeam/AdGuardHome/issues/2927
 [#2934]: https://github.com/AdguardTeam/AdGuardHome/issues/2934
@@ -87,6 +90,8 @@ and this project adheres to
 [#2954]: https://github.com/AdguardTeam/AdGuardHome/issues/2954
 [#2961]: https://github.com/AdguardTeam/AdGuardHome/issues/2961
 
+[doq-draft-02]: https://tools.ietf.org/html/draft-ietf-dprive-dnsoquic-02
+
 
 
 ## [v0.105.2] - 2021-03-10