Improve documentation for lua scripts

I had a hard time figuring out all the steps relevant for this to work.
Hopefully this brief summary and couple of links will help the next
person writing their own script.

See: #601

docs/rst/daemon/locations.rst

@@ -97,6 +97,8 @@ the parsing order matters in merging. See :ref:`config_conf_file_fragments`
    fragment files are *only* looked up in the directories specified by this
    variable.
 
+.. _config_locations_scripts:
+
 Location of scripts
 -------------------
 

docs/rst/index.rst

@@ -42,6 +42,7 @@ Table of Contents
 
    scripting/lua_api.rst
    scripting/existing_scripts.rst
+   scripting/custom_scripts.rst
 
 .. toctree::
    :maxdepth: 2

docs/rst/scripting/custom_scripts.rst

@@ -0,0 +1,41 @@
+.. _scripting_custom_scripts:
+
+Custom Scripts
+==============
+
+The locations where WirePlumber searches for scripts is explained in
+:ref:`config_locations_scripts`.
+
+Scripts are not loaded automatically; a component muse be defined for them, and
+this component must be included in a profile. See
+:ref:`config_components_and_profiles`.
+
+Full example
+------------
+
+Let's assume that ``~/.local/share/wireplumber/scripts/90-hello-world.lua``
+contains the following script:
+
+.. code-block:: lua
+
+   log = Log.open_topic("hello-world")
+   log.info("Hello world")
+
+In order for it to run, we'll define a component and include it in the default
+profile by including the following configuration (for example, in
+``~/.config/wireplumber/wireplumber.conf.d/90-hello-world.conf``):
+
+.. code-block::
+
+    wireplumber.components = [
+      {
+        name = "90-hello-world.lua", type = script/lua
+        provides = hello-world
+      }
+    ]
+
+    wireplumber.profiles = {
+      main = {
+        hello-world = required
+      }
+    }

docs/rst/scripting/meson.build

@@ -2,6 +2,7 @@
 sphinx_files += files(
   'lua_api.rst',
   'existing_scripts.rst',
+  'custom_scripts.rst',
 )
 
 subdir('lua_api')