add docs for new laikaRenderers setting

docs/src/02-running-laika/01-sbt-plugin.md

@@ -418,6 +418,36 @@ By default, the port is 4242, the poll interval is 3 seconds.
 With the `verbose` options the console will log all pages served.
 
 
+### Installing Additional Renderers
+
+The `laikaRenderers` setting holds the configurations for all of Laika's built-in renderers 
+and enables users to install their own or 3rd-party renderers.
+
+An example for installing a custom `indexFormat` renderer:
+
+```scala mdoc:compile-only
+import laika.api.format.*
+import laika.sbt.BinaryRendererConfig
+
+def indexFormat: TwoPhaseRenderFormat[Formatter, BinaryPostProcessor.Builder] = ???
+
+laikaRenderers += BinaryRendererConfig(
+  alias = "index",
+  format = indexFormat,
+  targetDirectory = (laikaSite / target).value / "search",
+  artifactBaseName = "searchIndex",
+  fileSuffix = "dat",
+  includeInSite = true,
+  supportsSeparations = false
+)
+```
+
+With the configuration above, the search index can be generated by calling `laikaGenerate index`
+(or together with other formats in one transformation - e.g. `laikaGenerate html index`).
+
+When the includeInSite property is true, the index will also be generated when calling `laikaSite`. 
+
+
 ### Inspecting Laika's Configuration
 
 Run `show laikaDescribe` to get a formatted summary of the active configuration,

sbt/src/main/scala/laika/sbt/LaikaPlugin.scala

@@ -41,9 +41,6 @@ import sbt.*
   *
   * - `Laika / excludeFilter`: files in the source directories to be excluded (default `HiddenFileFilter`)
   *
-  * - `laikaArtifactNameBuilder`: function that builds the name for artifacts (EPUB, PDF, ZIP) based on the provided
-  *   context info
-  *
   * - `laikaExtensions`: the main extension hook that allows to add one or more `ExtensionBundle` instances for adding
   *   directives, parser extensions, rewrite rules or custom renderers. See the API of `laika.api.bundle.ExtensionBundle`.
   *
@@ -58,8 +55,11 @@ import sbt.*
   * - `laikaTheme`: configuration for the theme to use for all transformations, if not specified the default
   *   `Helium` theme with all default colors and fonts will be used.
   *
+  * - `laikaRenderers`: contains the configurations for all of Laika's built-in renderers and enables users
+  *   to install their own or 3rd-party renderers.
+  *
   * - `laikaIncludeAPI`, `laikaIncludeEPUB` and `laikaIncludePDF`:
-  *   specifies whether to include scaladoc and/or PDF output in the generated site.
+  *   specifies whether to include scaladoc and/or PDF/EPUB output in the generated site.
   *
   * - `laikaDescribe`: inspects your setup and prints information about your inputs, outputs and installed extensions.
   *