Pull request: improve docs

Merge in DNS/adguard-home from update-docs to master

Squashed commit of the following:

commit 228c432adecf9f7927a692780a4762f1135b8cd6
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Nov 20 18:18:10 2020 +0300

    improve docs

CHANGELOG.md

@@ -9,18 +9,26 @@ and this project adheres to
 
 ## [Unreleased]
 
+<!--
+## [v0.105.0] - 2020-12-21
+-->
+
 ### Added
 
+- `$dnstype` modifier for filters [#2337].
 - HTTP API request body size limit [#2305].
 
 [#2305]: https://github.com/AdguardTeam/AdGuardHome/issues/2305
+[#2337]: https://github.com/AdguardTeam/AdGuardHome/issues/2337
 
 ### Changed
 
+- Our snap package now uses the `core20` image as its base [#2306].
 - Various internal improvements ([#2271], [#2297]).
 
 [#2271]: https://github.com/AdguardTeam/AdGuardHome/issues/2271
 [#2297]: https://github.com/AdguardTeam/AdGuardHome/issues/2297
+[#2306]: https://github.com/AdguardTeam/AdGuardHome/issues/2306
 
 
 

HACKING.md

@@ -47,6 +47,9 @@ The rules are mostly sorted in the alphabetical order.
  *  Document everything, including unexported top-level identifiers, to build
     a habit of writing documentation.
 
+ *  Constructors should validate their arguments and return meaningful errors.
+    As a corollary, avoid lazy initialization.
+
  *  Don't put variable names into any kind of quotes.
 
  *  Don't use naked `return`s.