Generate 'annotation' style plugin

[Sutharsan]

This adds a generator for a custom annotation style plugins: generate:plugin:type:annotation
The following files and directories is are being generated:

• src/Annotation/ExamplePlugin.php
• src/Plugin/ExamplePlugin/
• src/Plugin/ExamplePluginBase.php
• src/Plugin/ExamplePluginInterface.php
• src/Plugin/ExamplePluginManager.php
• module.services.yml

[Sutharsan]

This pull request is simpler than the one in pull request #499 and has less input options. But both add a custom plugin type with annotation discovery.

[jmolivas]

@Sutharsan: Thanks for the PR, I will be testing it later on today.

[jmolivas]

This looks great @Sutharsan. I run phpcs and this is the result of testing the drupal coding standards

FILE: ...pal8.dev/modules/custom/example/src/Plugin/ExamplePluginBase.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
----------------------------------------------------------------------
 17 | WARNING | [x] There must be no blank line following an inline
    |         |     comment
----------------------------------------------------------------------
PHPCBF CAN FIX THE 1 MARKED SNIFF VIOLATIONS AUTOMATICALLY
----------------------------------------------------------------------

FILE: ...dev/modules/custom/example/src/Plugin/ExamplePluginInterface.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
----------------------------------------------------------------------
 17 | WARNING | [x] There must be no blank line following an inline
    |         |     comment
----------------------------------------------------------------------
PHPCBF CAN FIX THE 1 MARKED SNIFF VIOLATIONS AUTOMATICALLY
----------------------------------------------------------------------

FILE: ...8.dev/modules/custom/example/src/Plugin/ExamplePluginManager.php
----------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
----------------------------------------------------------------------
 15 | ERROR | [x] Doc comment short description must start with a
    |       |     capital letter
----------------------------------------------------------------------
PHPCBF CAN FIX THE 1 MARKED SNIFF VIOLATIONS AUTOMATICALLY
----------------------------------------------------------------------

Time: 56ms; Memory: 4.75Mb

The error is generated from line 19 at templates/module/src/plugin-type-annotation-manager.php.twig

A solution could be update current code

/**
 * {{ label }} plugin manager.
 */

With:

/**
 * Provides the {{ label }} plugin manager.
 */

[Sutharsan]

Done.