Update TechDocs documentation, overview, gettings started, support status, concepts, etc.

1. Add a table of all the platforms that are supported and that are in pipeline. Add issue to trac
k their progress.
2. Update concepts about publisher, and add preparer and generator
3. Getting started is now complete, describes both backend and frontend, and has better setting the configuration section.
4. Some typos and code comments

packages/backend/src/plugins/techdocs.ts

@@ -32,10 +32,7 @@ export default async function createPlugin({
   discovery,
   reader,
 }: PluginEnvironment) {
-  const generators = new Generators();
-  const techdocsGenerator = new TechdocsGenerator(logger, config);
-  generators.register('techdocs', techdocsGenerator);
-
+  // Preparers are responsible for fetching source files for documentation.
   const preparers = new Preparers();
 
   const directoryPreparer = new DirectoryPreparer(logger);
@@ -49,8 +46,17 @@ export default async function createPlugin({
   const urlPreparer = new UrlPreparer(reader, logger);
   preparers.register('url', urlPreparer);
 
+  // Generators are used for generating documentation sites.
+  const generators = new Generators();
+  const techdocsGenerator = new TechdocsGenerator(logger, config);
+  generators.register('techdocs', techdocsGenerator);
+
+  // Publishers are used for
+  // 1. Publishing generated files to storage
+  // 2. Fetching files from storage and passing them to TechDocs frontend.
   const publisher = Publisher.fromConfig(config, logger, discovery);
 
+  // Docker client used by the generators.
   const dockerClient = new Docker();
 
   return await createRouter({