Add description field to ParagraphType

Awesome, let's get this in.

But a littlebit of test coverage (one single desc, one single assert) is a requirement. :-)

Tested this and works fine. Just small improvements:

1. +++ b/src/Entity/ParagraphsType.php
   @@ -156,6 +164,14 @@ class ParagraphsType extends ConfigEntityBundleBase implements ParagraphsTypeInt
   +
   

   One extra blank line.

2. +++ b/src/Tests/Classic/ParagraphsTypesTest.php
   @@ -73,4 +73,30 @@ class ParagraphsTypesTest extends ParagraphsTestBase {
   +    $this->assertText("Saved the $label Paragraphs type.");
   

   We can add here one more assert to check if $description is displayed in 'DESCRIPTION' column after saving.

1. +++ b/src/ParagraphsTypeInterface.php
   @@ -53,6 +53,14 @@ interface ParagraphsTypeInterface extends ConfigEntityInterface {
      /**
   +   * Gets the description.
   +   *
   +   * @return string
   +   *   The description of this node type.
   +   */
   +  public function getDescription();
   

   The @return documentation should be The description of this paragraphs type..

2. +++ b/src/Tests/Classic/ParagraphsTypesTest.php
   @@ -73,4 +73,34 @@ class ParagraphsTypesTest extends ParagraphsTestBase {
   +    //Check if description is at Description column
   +    $header = count($this->xpath('//table/thead/tr/th[.="Description"]/preceding-sibling::th'));
   +    $row = count($this->xpath('//table/tbody/tr/td[.="' . $description . '"]/preceding-sibling::td'));
   +    $this->assertEqual($header, $row);
   

   This checks that the description is under the description header, if both exists.
   But it also passes, if there is no description and no description header.

   What we need is a simple

   $this->assertText("Description");
   $this->assertText($description);
   

   .

   Also, maybe it's better to rename $header to $header_position and $row to $row_position, or similar, to make it clearer in the variable names what is actually being checked here.

I think this looks good.

Thank you for your work!

Very nice, committed. :-)
Now let's add those descriptions to the existing demo / collection paragraph types.

@aheredia I attributed VladimirMarko and toncic for reviewing the patches and giving feedback. That's a key type of contribution.
Even if you would provide 100% perfect patches and someone does a QUALIFIED review with proper statement and setting it to RTBC, i would attribute that person.

I seem to accidentally have switched the patch author to VladimirMarko, i intended to keep you there.
To "fix" authoring, i pushed an empty commit with the proper author setting, so it can show up in your commit list.