upgrade file-structure file

Author: arhimede

docs/book/v4/introduction/file-structure.md

@@ -1,22 +1,30 @@
 # File structure
 
-It is a good practice to standardize the file structure of projects. This way it’s easier to keep a clean overview of multiple projects, and less time is wasted trying to find the correct class.
+Dotkernel API follows the [PSR-4](https://www.php-fig.org/psr/psr-4/) standards.
 
-When using DotKernel API the following structure is recommended:
+It is a good practice to standardize the file structure of projects.
+
+When using DotKernel API the following structure is installed by default:
+
+![Dotkernel API File Structure!](https://docs.dotkernel.org/img/api/file-structure-dk-api.png)
 
 ## Main directories
 
-* `src` - should contain the source code files
-* `templates` - should contain the page templates and layouts
+* `bin` - executable files from CLI
+* `config` - various configuration files
 * `data` - should contain project-related data (AVOID storing sensitive data on VCS)
-* `docs` - should contain project-related documentation
+* `documentation` - should contain project-related documentation
+* `log` - storage of log files generated by dot-error-log library
+* `public` - publicly visible files. The webserver need to have this folder as www-document root folder.
+* `src` - should contain the source code files
+* `test` - should contain the test files
 
-These directories reside in one of the following directories:
+## Special purpose folders
 
-* if the Module is a composer package where the directories above are stored in the package’s root path, eg.: `/vendor/my-name/my-project-name/`
-* if the Module is an extension/component for the project, eg.: `/src/MyProjectName`
+* `.github`  - containes workflow files
+* `.laminas-ci` - contains laminas-ci workflow files
 
-## The `src` directory
+## `src` directory
 
 This directory contains all source code related to the Module. It should contain following directories, if they’re not empty:
 
@@ -35,20 +43,19 @@ The `src` directory should also contain 2 files:
 * `ConfigProvider.php` - Provides configuration data
 * `RoutesDelegator.php` - Module main routes entry file
 
-## The `templates` directory
+## `templates` directory
 
 This directory contains the template files, used for example to help render e-mail templates.
 
 > DotKernel API uses twig as Templating Engine. All template files have the extension .html.twig
 
-## The `data` directory
+## `data` directory
 
 This directory contains project-related data (such as cache, file uploads)
 
 We recommend using the following directory structure:
 
 * `data/cache` - location where caches are stored
 * `data/oauth` - encryption, private and public keys needed for authentication.
-* `data/lock` - folder where lock files generated by commands are stored, if enabled
-* `data/doctrine/fixtures` - folder for doctrine data fixtures
-* `data/doctrine/migrations` - folder for doctrine migrations
+* `data/doctrine` - fixtures and migrations 
+* `data/lock` - lock files generated by `dotkernel/dot-cli`  [See more](https://docs.dotkernel.org/dot-cli/v3/lock-files/)