Pull request: * home, openapi: improve docs and responses

Merge in DNS/adguard-home from 2243-better-docs to master

Closes #2243.

Squashed commit of the following:

commit 26c655a0e4339528870633c2cdf39c3b5c486b1d
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Nov 5 12:51:43 2020 +0300

    * openapi: improve more

commit dc0ab9857787d14eb0686814a4f3c8f917698bee
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Nov 3 20:40:32 2020 +0300

    * home, openapi: improve docs and responses

openapi/README.md

@@ -1,25 +1,35 @@
-## AdGuard Home OpenAPI
+# AdGuard Home OpenAPI
 
-We are using [OpenAPI specification](https://swagger.io/docs/specification/about/) to generate AdGuard Home API specification.
+We are using
+[OpenAPI specification](https://swagger.io/docs/specification/about/)
+to generate AdGuard Home API specification.
 
-### How to edit the API spec
+## How To Edit The API Spec
 
-The easiest way would be to use [Swagger Editor](http://editor.swagger.io/) and just copy/paste the YAML file there.
+The easiest way would be to use
+[Swagger Editor](http://editor.swagger.io/)
+and just copy/paste the YAML file there.
 
-### How to read the API doc
+## How To Read The API Doc
 
 1. `yarn install`
 2. `yarn start`
 3. Open `http://localhost:4000/`
 
-### Changelog
+## Changelog
 
-[Here](CHANGELOG.md) we keep track of all non-compatible changes that are being made.
+[Here](CHANGELOG.md) we keep track of all non-compatible changes that are being
+made.
 
-### Authentication
+## Authentication
 
-If AdGuard Home's web user is password-protected, a web client must use authentication mechanism when sending requests to server.  Basic access authentication is the most simple method - a client must pass `Authorization` HTTP header along with all requests:
+If AdGuard Home's web user is password-protected, a web client must use
+authentication mechanism when sending requests to server.  Basic access
+authentication is the most simple method - a client must pass `Authorization`
+HTTP header along with all requests:
 
-    Authorization: Basic BASE64_DATA
+```http
+Authorization: Basic BASE64_DATA
+```
 
-where BASE64_DATA is base64-encoded data for `username:password` string.
+Where BASE64_DATA is base64-encoded data for `username:password` string.

openapi/openapi.yaml

@@ -1137,9 +1137,18 @@ components:
             type: object
             description: Filtering URL settings
             properties:
+                data:
+                    properties:
+                        enabled:
+                            type: boolean
+                        name:
+                            type: string
+                        url:
+                            type: string
+                    type: object
                 url:
                     type: string
-                enabled:
+                whitelist:
                     type: boolean
         FilterRefreshRequest:
             type: object
@@ -1466,6 +1475,8 @@ components:
                     description: URL or an absolute path to the file containing filtering rules
                     type: string
                     example: https://filters.adtidy.org/windows/filters/15.txt
+                whitelist:
+                    type: boolean
         RemoveUrlRequest:
             type: object
             description: /remove_url request data