Documentation translation (#199)

Documentation translation using weblate.

* Use po4a to generate .po files from the english markdowns, then to generate translated files
* Some pages can be marked as «english only» (for technical documentation for example)
* New Hugo shortcode to use application strings in documentation (for example for settings names)
* The code of conduct is no more translated, but there is a link to official Contributor Covenant translations
* Adding all plugin's supported languages

Related to https://github.com/JohnXLivingston/peertube-plugin-livechat/issues/117

support/documentation/content/en/documentation/user/_index.md

@@ -0,0 +1,8 @@
+---
+title: "User documentation"
+description: "Plugin peertube-plugin-livechat user documentation"
+weight: 40
+chapter: false
+---
+
+{{% children depth="3" style="li" description="true" %}}

support/documentation/content/en/documentation/user/moderation.md

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+---
+title: "Moderation"
+description: "Plugin peertube-plugin-livechat moderation"
+weight: 10
+chapter: false
+---
+
+You can access room settings and moderation tools by opening the chat in a new window,
+and using the dropdown menu at the top right.
+
+You can list all existing chatrooms: in the plugin settings screen, there is a button «List rooms».
+
+You can delete old rooms: join the room, and use the menu on the top to destroy the room.
+
+## Notes
+
+All instance moderators and admins will be owner of created chat rooms.
+If the video is local (not from a remote Peertube), the video owner will be admin in the chat room.
+
+You can use [ConverseJS moderation commands](https://conversejs.org/docs/html/features.html#moderating-chatrooms) to moderate the room.
+When you open the chat room in full screen, there will also be a menu with dedicated commands on the top right.

support/documentation/content/en/documentation/user/obs.md

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+---
+title: "OBS"
+description: "Documentation to stream the chat content using OBS."
+weight: 10
+chapter: false
+---
+
+## OBS Overlay
+
+If you are using OBS for streaming, you can easily include the chat in your stream.
+
+You can use the «share chat link» feature to generate an URL to your chat.
+The button should be near the chat if you are the video owner (unless it was desactivated by your server admins).
+
+Check the «readonly» checkbox in the modal.
+Then use this link as a «web browser source» in OBS.
+
+You can use the «Transparent background» to have a transparent background in OBS.
+If you want to customize the background transparency, you can add this CSS in your OBS browser source's settings:
+
+```css
+:root {
+  --livechat-transparent: rgba(255 255 255 / 90%) !important;
+}
+```
+
+Note: you can customize colors. This is undocumented yet, but you can try this:
+in the modal, check «use curent theme colors», then you can try to manually change color values in the URL.
+You must use valid CSS color values, and they must be properly URL encoded.
+
+## Mixing multiple chats in your live stream
+
+You can use the [social_stream browser extension](https://github.com/steveseguin/social_stream#readme) to mix multiple chat source (from Peertube, Twitch, Youtube, Facebook, ...) and include their contents in your live stream.
+The compatibility with this plugin was added in recent versions.

support/documentation/content/en/documentation/user/xmpp_clients.md

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+---
+title: "XMPP Clients"
+description: "Connect to chat using a XMPP client"
+weight: 40
+chapter: false
+---
+
+This chat plugin relies on the XMPP protocol (also known as Jabber).
+It is therefore possible to connect to the chats using
+[XMPP client software](https://en.wikipedia.org/wiki/XMPP#Clients).
+This can be useful for example to facilitate moderation operations.
+
+{{% notice info %}}
+The features described on this page must be enabled and configured by
+your Peertube instance's administrators. You may therefore not have access to them.
+{{% /notice %}}
+
+## Login to your Peertube account
+
+{{% notice warning %}}
+This feature is not yet available, and will come in a future version of the plugin.
+{{% /notice %}}
+
+## Connection using an external XMPP account
+
+If this feature is enabled on your instance, you can connect to Peertube
+chats using any XMPP account.
+
+To get the address of the room you want to join, you can use the "share chat"
+button that is located above the chat:
+
+![Share button](/peertube-plugin-livechat/images/share_button.png?classes=shadow,border&height=200px)
+
+{{% notice info %}}
+By default, the share button is only visible to the owner of the video,
+and the admins/moderators of the instance.
+However, admins can decide to display this button for everyone.
+{{% /notice %}}
+
+Then, choose "Connect using XMPP":
+
+![Share XMPP](/peertube-plugin-livechat/images/share_xmpp_dialog.png?classes=shadow,border&height=200px)
+
+Then you just have to click on "open" or copy/paste the address of the chat room into your XMPP client
+(using the "join a room" feature).