feat: custom project commands

Enable defining custom cli commands in project, not just plugins.

Author: corvidism

packages/cli/src/commands/userDefined.mjs

@@ -29,6 +29,10 @@ const existsMerkurConfig = fs
   .includes('merkur.config.mjs');
 
 if (existsMerkurConfig) {
+  const projectCommandsDir = path.resolve(process.cwd(), 'commands');
+  if (fs.existsSync(projectCommandsDir)) {
+    await extendCommandsFromDir(projectCommandsDir);
+  }
   const merkurDir = path.resolve(process.cwd(), 'node_modules/@merkur');
   if (fs.existsSync(merkurDir)) {
     let dirs = fs.readdirSync(merkurDir);

website/docs/register-custom-element.md

@@ -22,7 +22,7 @@ The default Merkur template is prepared for SSR. In the following sections, we w
 
 ### Server part
 
-After creating a new Merkur widget, update your playground template by creating the `/server/playground/templates/body.ejs` and `/server/playground/templates/footer.ejs` files. You can also run `merkur custom playground:body` and `merkur custom playground:footer` to generate these files. Then, modify the files as follows:
+After creating a new Merkur widget, run `merkur custom playground:body` and `merkur custom playground:footer` to make local copies of the playground files and modify them as follows:
 
 ```javascript
 // body.ejs