Envision: add plugins section

content/docs/fossvr/envision/_index.md

@@ -25,7 +25,7 @@ You can download the latest AppImage snapshot from [GitLab Pipelines](https://gi
 
 If you are on Arch, You can use the [AUR package](https://aur.archlinux.org/packages/envision-xr-git) `envision-xr-git`
 
-## Getting Started
+## Getting started
 
 Upon launching Envision, you will need to select a profile on the bottom of the left side bar.
 
@@ -40,7 +40,36 @@ Profiles that are available by default:
 
 Monado does not have a launcher app, and so after connecting your headset, you will likely see a solid color. This means you can now start your VR title.
 
-You may want to launch [WlxOverlay-S](/docs/fossvr/wlxoverlay-s/) first and use it to access your desktop and other VR titles. You can even start it automatically alongside the Monado session: just enter `wlx-overlay-s --openxr` into the "Autostart" field of your Envision profile.
+You may want to launch [WlxOverlay-S](/docs/fossvr/wlxoverlay-s/) first and use it to access your desktop and other VR titles. You can even start it automatically alongside the Monado/WiVRn session, by enabling it in the [Plugins](#plugin-system) menu.
+
+## Plugin system
+
+The plugin system for Envision allows you to launch anything (usually OpenXR overlays) alongside the Monado/WiVRn session.
+
+Open the Plugins window by clicking the kebab menu (three dots) at the top of the Envision window, and clicking "Plugins". Here, you can install overlays like [WlxOverlay-S](/docs/fossvr/wlxoverlay-s) or [Stardust XR](/docs/fossvr/stardust) (or a custom plugin — see below). After installing plugins and toggling them on, once you start a profile, the enabled plugins will start alongside it.
+
+Plugins are the replacement for the "autostart" feature from older versions.
+
+### Adding a custom plugin
+
+The plugins included in the store are just a quick front-end to the latest release AppImages. For everything else, you can create a custom plugin that runs any given executable script or binary.
+
+For example, if you installed WlxOverlay-S from AUR or built it from source, you can disable the original WlxOverlay-S plugin and create a custom plugin to run it:
+
+1. Create a new file `~/.local/bin/wlx-but-newer` (creating the `~/.local/bin` directory if it does not exist).
+2. Give it the content:
+    ```bash
+    #!/usr/bin/env bash
+    /usr/bin/wlx-overlay-s --openxr
+    ```
+3. `chmod +x ~/.local/bin/wlx-but-newer`
+4. In Envision, open the Plugins window.
+5. Add a custom plugin by clicking the ➕ plus button.
+6. For the executable file, point it to the script you just created.
+7. Name the plugin "Wlx but newer".
+8. Save, and then enable the new plugin.
+
+Now starting the profile will also start your custom or AUR version of WlxOverlay-S.
 
 ## Experimental feature settings
 
@@ -48,7 +77,7 @@ The following resources can be entered into your Envision profile repo and branc
 
 ### Full body Lighthouse tracking
 
-Full body is now provided by default in Monado & OpenComposite through the XR_MNDX_xdev_space OpenXR vendor extension. This allows any tracked "xdev" in Monado to be forwarded as a raw pose without bindings to applications. OpenComposite exposes these as fake Vive FBT trackers for use.
+Full body is no longer experimental; it is enabled by default in Monado & OpenComposite through the XR_MNDX_xdev_space OpenXR vendor extension. This allows any tracked "xdev" in Monado to be forwarded as a raw pose without bindings to applications. OpenComposite exposes these as fake Vive FBT trackers for use.
 
 ### WMR & Rift S controller tracking