[Docs] Replace recommonmark with MyST parser

We used recommonmark so that we can use markdown in sphinx but it is
buggy and now so switch to better supported MyST-parser.

* Fixed incorrect heading warnings in markdown.
* Added sphinx toctree to markdown using directive as required by MyST.
* Upgraded Sphinx to 4.3

Ref: https://myst-parser.readthedocs.io

docs/source/how-to/index.md

@@ -4,7 +4,11 @@ A collection of guides covering common issues that might be encountered using De
 
 ## GTK UI
 
-- [Set default torrent application](set-mime-type.md)
+```{toctree}
+:titlesonly:
+
+Set default torrent application <set-mime-type>
+```
 
 ## Deluge as a service
 
@@ -14,6 +18,10 @@ shutdown and automatically restart them if they crash.
 
 The Deluge daemon deluged and Web UI deluge-web can both be run as services.
 
-- [Create systemd services for Linux](systemd-service.md)
-- [Create launchd services for macOS](launchd-service.md)
-- [Create NSSM services for Windows](nssm-service.md)
+```{toctree}
+:titlesonly:
+
+Create systemd services for Linux <systemd-service>
+Create launchd services for macOS <launchd-service>
+Create NSSM services for Windows <nssm-service>
+```

docs/source/how-to/launchd-service.md

@@ -12,7 +12,7 @@ and will need modified if using other installation methods e.g. `Deluge.app`.
 Create the file `/Library/LaunchDaemons/org.deluge-torrent.deluged.plist`
 containing the following:
 
-```eval_rst
+```{eval-rst}
 .. literalinclude:: ../../../packaging/osx/launchd/org.deluge-torrent.deluged.plist
     :language: xml
 ```
@@ -29,7 +29,7 @@ sudo launchctl start org.deluge-torrent.deluged
 Create the file `/Library/LaunchDaemons/org.deluge-torrent.deluge-web.plist`
 containing the following:
 
-```eval_rst
+```{eval-rst}
 .. literalinclude:: ../../../packaging/osx/launchd/org.deluge-torrent.deluge-web.plist
     :language: xml
 ```

docs/source/how-to/systemd-service.md

@@ -30,7 +30,7 @@ sudo adduser <username> deluge
 
 Create the file `/etc/systemd/system/deluged.service` containing the following:
 
-```eval_rst
+```{eval-rst}
 .. literalinclude:: ../../../packaging/systemd/deluged.service
     :language: ini
 ```
@@ -47,7 +47,7 @@ sudo mkdir /etc/systemd/system/deluged.service.d/
 Then create a user file `/etc/systemd/system/deluged.service.d/user.conf` with
 the following contents:
 
-```eval_rst
+```{eval-rst}
 .. literalinclude:: ../../../packaging/systemd/user.conf
     :language: ini
 ```
@@ -82,7 +82,7 @@ after changes.
 
 Create the file `/etc/systemd/system/deluge-web.service` containing the following:
 
-```eval_rst
+```{eval-rst}
 .. literalinclude:: ../../../packaging/systemd/deluge-web.service
     :language: ini
 ```
@@ -99,7 +99,7 @@ sudo mkdir /etc/systemd/system/deluge-web.service.d/
 Then create a user file `/etc/systemd/system/deluge-web.service.d/user.conf` with
 the following contents:
 
-```eval_rst
+```{eval-rst}
 .. literalinclude:: ../../../packaging/systemd/user.conf
     :language: ini
 ```