Website: document a bit more about job compiler scripts

web/project-website/content/usage/job-compiler-scripts/_index.md

@@ -3,10 +3,57 @@ title: Job Compiler Scripts
 weight: 10
 ---
 
-TODO: write this :)
+Flamenco uses *job compiler scripts* to convert a job definition (like "*render
+this Blend file*") into concrete tasks that can be executed by workers.
+
+## Example
+
+These scripts are written in JavaScript. Before describing how they work, here
+is a simple example that just logs a message (one task) and sleeps for a bit
+(another task):
+
+```JavaScript
+const JOB_TYPE = {
+    label: "Log and Sleep",
+    settings: [
+        { key: "message", type: "string", required: true },
+        { key: "sleep_duration_seconds", type: "int32", default: 1 },
+    ]
+};
+
+function compileJob(job) {
+    const settings = job.settings;
+
+    const echoTask = author.Task("echo", "misc");
+    echoTask.addCommand(author.Command("echo", {
+        message: settings.message,
+    }));
+    job.addTask(echoTask);
+
+    const sleepTask = author.Task("sleep", "misc")
+    sleepTask.addCommand(author.Command("sleep", {
+        duration_in_seconds: settings.sleep_duration_seconds,
+    }))
+    job.addTask(sleepTask);
+}
+```
+
+Each job compiler has two parts to it:
+
+- the `JOB_TYPE` that defines the settings and how it's shown in the Blender add-on, and
+- the `compileJob()` function that takes those settings and creates the tasks.
+
+TODO: write more documentation. For now, you can refer to [the built-in job
+compiler scripts](built-in-scripts) as examples.
+
+[built-in-scripts]: https://developer.blender.org/diffusion/F/browse/main/internal/manager/job_compilers/scripts/
 
 ## Task Types
 
+In the above example code, you can see calls like `author.Task("echo", "misc")`.
+The first parameter is the task name, which will be shown in the web interface
+and can help to identify each task. The second parameter is the *task type*.
+
 The following task types are defined by the standard job compiler scripts:
 
 - `blender`: any task that runs Blender.
@@ -15,3 +62,15 @@ The following task types are defined by the standard job compiler scripts:
   renders out of the way to make place for new ones, etc.
 - `misc`: tasks mostly used for testing things, such as "log a debug message" or
   "do nothing for 5 seconds".
+
+These can be used to determine which worker executes which task. For example,
+let a puny machine do the file management and maybe video compression with
+FFmpeg, while the Blender tasks are left for the big ones. By default the
+workers can run all the above task types. See [worker
+configuration][worker-config] for more info.
+
+In the end, these are just strings. When you create your own job compiler
+scripts, you can follow these types or make them up yourself. Don't forget to
+configure your workers to run them!
+
+[worker-config]: {{< ref "usage/worker-configuration" >}}