[docs] DDEV project type (#7)

* remove EOL whitespace

* add blank line after heading

* Add a troubleshooting section

---------

Co-authored-by: tyler36 <7234392+tyler36@users.noreply.github.com>

Author: tyler36

README.md

@@ -2,18 +2,20 @@ DDEV integration for developing Drupal contrib projects. As a general philosophy
 
 Install
 ===========
+
 1. `git clone` your contrib module
 2. [Add DDEV to your contrib project](https://ddev.readthedocs.io/en/latest/users/project/) if not already added.
 3. Run `ddev get ddev/ddev-drupal-contrib`.
 
 Commands
 ============
+
 This project provides the following DDEV container commands.
 
-- [ddev poser](https://github.com/ddev/ddev-drupal-contrib/blob/main/commands/web/poser). 
-  - Edits composer.json so that `drupal/core-recommended` becomes a dev dependency. 
-  - Runs `composer install` AND `yarn install` so that dependencies are available. 
-  - Note: it is perfectly acceptable to skip this command and edit the require-dev of composer.json by hand. 
+- [ddev poser](https://github.com/ddev/ddev-drupal-contrib/blob/main/commands/web/poser).
+  - Edits composer.json so that `drupal/core-recommended` becomes a dev dependency.
+  - Runs `composer install` AND `yarn install` so that dependencies are available.
+  - Note: it is perfectly acceptable to skip this command and edit the require-dev of composer.json by hand.
 - [ddev symlink-project](https://github.com/ddev/ddev-drupal-contrib/blob/main/commands/web/symlink-project). This symlinks the top level files of your project into web/modules/custom so that Drupal finds your module. This command runs automatically on every `ddev start`. See codebase image below.
 - `ddev phpunit`. Run phpunit tests on the web/modules/custom directory.
 - `ddev nightwatch`. Run nightwatch tests on the web/modules/custom directory.
@@ -28,12 +30,25 @@ Codebase layout
 
 Misc
 =======
+
 - Optional: [Install Chrome service for FunctionalJavascript and Nightwatch tests](https://github.com/ddev/ddev-selenium-standalone-chrome).
 - Optional. Commit the changes .ddev after this plugin installs. This saves other users from having to install this integration. Rerun the `ddev get` in order to update the commands from this project.
 - This project reads your `project_type` from DDEV and fetches adds the corresponding version of `drupal/core-recommended` to composer.json. if you are doing something non-standard with project_type, don't use `ddev poser` command.
 - This project should work for any contrib project, including those that haven't [opted into Gitlab CI](https://www.drupal.org/project/infrastructure/issues/3261803). One advantage of that is that failures in CI are more likely to be reproducible locally when using this integration.
-- If you add/remove a root file or directory, re-symlink root files via EITHER of these methods 
+- If you add/remove a root file or directory, re-symlink root files via EITHER of these methods
   - `ddev restart`
   - `ddev symlink-project`
 
+Troubleshooting
+=======
+
+"Error: unknown command":
+
+The commands from this addon are available when the project type a valid `drupal` type.
+Below, is an example `.ddev/config.yaml` for a Drupal 10 project.
+
+```yaml
+type: drupal10
+```
+
 **Contributed and maintained by [@weitzman](https://github.com/weitzman)**