[docs] big bang update (#348)

* [docs] big bang update

* Simplified polluted README.md by moving parts to the documentation
* Removed duplicates with `pymdownx.snippets` extension
* Enabled code copy
* Extended "Getting Started"
* Added "Monitoring" page
* Separated "Upgrade" page
* Added default config yaml to docs

Signed-off-by: Dmytro Bondar <git@bonddim.dev>

* Update sources.md

Co-authored-by: h44z <christoph.h@sprinternet.at>

---------

Signed-off-by: Dmytro Bondar <git@bonddim.dev>
Co-authored-by: h44z <christoph.h@sprinternet.at>

docs/documentation/getting-started/docker.md

@@ -5,20 +5,7 @@ The preferred way to start WireGuard Portal as Docker container is to use Docker
 A sample docker-compose.yml:
 
 ```yaml
-version: '3.6'
-services:
-  wg-portal:
-    image: wgportal/wg-portal:latest
-    restart: unless-stopped
-    cap_add:
-      - NET_ADMIN
-    network_mode: "host"
-    ports:
-      - "8888:8888"
-    volumes:
-      - /etc/wireguard:/etc/wireguard
-      - ./data:/app/data
-      - ./config:/app/config
+--8<-- "docker-compose.yml::17"
 ```
 
 By default, the webserver is listening on port **8888**.
@@ -31,6 +18,7 @@ All images are hosted on Docker Hub at [https://hub.docker.com/r/wgportal/wg-por
 There are three types of tags in the repository:
 
 #### Semantic versioned tags
+
 For example, `1.0.19`.
 
 These are official releases of WireGuard Portal. They correspond to the GitHub tags that we make, and you can see the release notes for them here: [https://github.com/h44z/wg-portal/releases](https://github.com/h44z/wg-portal/releases).
@@ -44,16 +32,17 @@ If you only want to stay at the same major or major+minor version, use either `v
 Version **1** is currently **stable**, version **2** is in **development**.
 
 #### latest
+
 This is the most recent build to master! It changes a lot and is very unstable.
 
 We recommend that you don't use it except for development purposes.
 
 #### Branch tags
+
 For each commit in the master and the stable branch, a corresponding Docker image is build. These images use the `master` or `stable` tags.
 
-
-
 ## Configuration
+
 You can configure WireGuard Portal using a yaml configuration file.
 The filepath of the yaml configuration file defaults to `/app/config/config.yml`.
 It is possible to override the configuration filepath using the environment variable **WG_PORTAL_CONFIG**.
@@ -61,6 +50,7 @@ It is possible to override the configuration filepath using the environment vari
 By default, WireGuard Portal uses a SQLite database. The database is stored in `/app/data/sqlite.db`.
 
 You should mount those directories as a volume:
+
 - /app/data
 - /app/config